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DESCRIPTIVE 

GENERAL CHEMISTRY 



A TEXT-BOOK FOR SHORT COURSE. 



BY 



S. E. TILLMAN, 

Professor of Chemistry, Mineralogy, and Geology, 
United States Military Academy. 



FOURTH EDITION, REVISED AND ENLARGED. 
FIRST THOUSAND. 



NEW YORK: 

JOHN WILEY & SONS. 

London : CHAPMAN & HALL, Looted. 

1907 



U»hAHY«f CONGRESS 
I wo Cootes Received 

SEP10'90f 

. Copyncht Bntry 

cusi A / XXC., No, 
COPY B. 






Copyright, 1897, 1899, 1907, 

BY 

8. E. TILLMAN. 



ROBERT DRtTMMOND, PRINTER, NEW YORK. 



PREFACE, 



In adding another to the long list of chemical text- 
books already in existence, it is appropriate for, if not 
incumbent upon, the author to give some explanation for 
his action. The influencing causes, together with the gov- 
erning conditions and the objects attempted, will there- 
fore be briefly outlined. 

Chemical instruction has been given at the Military 
Academy for nearly eighty years. The experience and 
judgment of the Academic Board (Faculty) and of their 
military superiors has from the outset limited this instruc- 
tion to a very short course, the time now devoted to it 
being about two months, and this has been substantially 
the same for many years. The actual time of the student 
available is a little less than two hundred hours for in- 
struction, study, and other work in the subject. 

The problem and effort of this department has ever been 
to provide the most appropriate instruction in this short 
course for students who are to become professional soldiers, 
and who approach the science well disciplined in habits of 
study and well grounded in the ordinary mathematical 
processes. It is thought that a great majority of those who 
have had experience in chemical teaching will agree that 
the unique disciplinary training for which chemistry is so 
admirably adapted as a laboratory science could be only 
very imperfectly attained under the conditions. 

It has generally been the conclusion of those charged 
with this instruction at the Academy in the past that the 
laboratory method alone, or mainly, in so short a coarse, 
could not be made of as much value to the pupils as the 
method making the acquisition of knowledge the essential 



iv PREFACE, 

feature, and that the best results could be reached through 
careful study of the proper text, well-conducted recitations, 
accompanied by experimental and explanatory lectures. 
While accepting the general correctness of this conclusion 
of the past, the author would add a small amount of well- 
selected laboratory practice on the part of the student, 
this practice being intended as much for sustaining and 
increasing interest in study and for fixing principles in 
mind as for strictly laboratory discipline. 

The information given should be that most useful, im- 
proving, and gratifying to educated men. The decision as to 
that which is most beneficial and desirable for military 
students has been made through the assistance and sugges- 
tion of many officers who have acted as instructors in the 
department, after experience in the different arms of the 
military service. In the opinion of the author, however, 
the chemical knowledge most requisite to the average pro- 
fessional soldier differs but little from that essential to 
other educated men. 

While it is desirable, under the conditions, to give the 
educational element of information great prominence, it is 
advocated that, by the proper system and sequence, the 
acquisition of the knowledge can be made to involve a high 
order of mental training ; indeed, in a science so compre- 
hensive, involving so many facts and such a variety of 
useful applications, the one cannot be remembered nor the 
other comprehended except through scientific method of 
great disciplinary value. 

In the efforts to best meet the imposed requirements and 
conditions no single text-book has been found entirely 
suitable, though many have been carefully examined and 
tested. Some books contain substantially all the desired 
matter, but usually much other that cannot be used. The 
lack of the desired arrangement of the matter is another 
important difficulty to be overcome. In all chemical text- 



PREFACE. v 

books used at the Academy many omissions, insertions, and 
transpositions have been found necessary. The necessity 
for such changes adds greatly to the difficulties of the stu- 
dent in accomplishing what is expected from him. 

This book has been prepared to embody the substance 
and arrangement of a short chemical course for the general 
student. It aims to give a concise statement of the more 
fundamental principles of chemistry, together with that 
class of chemical information most essential to cultured 
men, and which will enable them to comprehend many 
ordinary natural phenomena as well as to understand the 
more important applications of the science which are now 
so frequently met with. The book is not fitted nor in- 
tended for laboratory guidance. 

The arrangement adopted in the book is that which long 
experience and careful consideration have shown to accom- 
plish the best results with students equipped as ours are, 
in the time available. 

The first chapter contains much that is often classed as 
"theoretical chemistry" but in the opinion of the author, 
with the limitations of language observed throughout, the 
contents of this chapter are essential to every one expecting 
to derive the highest benefit from even a general course of 
descriptive and applied chemistry. This opinion is based 
upon the belief that advantage should be taken of every 
approach made by chemical science to exactness, and its 
processes made deductive when possible. The chapter in- 
volves no ideas nor deductions that cannot be readily 
grasped by fairly equipped students. 

The second chapter includes a statement of some of the 
more recent conclusions as to influencing causes in chemi- 
cal processes, and of the Periodic Law, all of which, it is 
believed, are destined to become important factors in estab- 
lishing a scientific foundation and system of chemistry. 
The contents of this chapter are not at present essential to 



vi PREFACE. 

the general student of a short course, but it is thought that 
they will be found easily intelligible, interesting, and very 
suggestive. 

The classification of the elements into metallic and non- 
metallic has been retained, as, upon the whole, involving 
more advantages and fewer difficulties than any other for 
the limited course. The non-metals are described in the 
third chapter, and the metals in the fourth. 

The relative importance of subjects in a short general 
course permits only brief reference to the extended class of 
carbon compounds. In chapter five certain of these com- 
pounds, deemed most important in a general or professional 
way, are described and discussed. 

In chapter six are given some of the more important 
industrial applications of chemistry, with statement of the 
principles involved, which could not be as appropriately 
included in previous chapters. 

Throughout the book American processes are referred 
to as far as practicable to illustrate the useful application 
of chemical principles, or in describing processes by which 
bodies are obtained, as in the metallurgy of iron, copper, 
lead, etc. 

The two sizes of type employed in the text are intended 
to emphasize the relative importance of the matter and to 
facilitate the assignment of the portions more important 
for study. The matter in fine print is of comparatively lit- 
tle importance to the general student. 

Only such figures are introduced into the book as are 
typically important or aid in elucidating the descriptive 
text. The figures, with few exceptions, are from original 
drawings. For the preparation of the figures I am in- 
debted to my former assistants, Lieut. Edgar Kussel and 
Lieut, W. B, Smith. 

S. E. T. 

West Point N. Y., June, 1899. 



PREFACE TO THIRD EDITION. 



The necessity for a new edition of this book has 
enabled the author to correct all typographical errors dis- 
covered in the edition of 1899. It has also given oppor- 
tunity to make use of the suggestions contained in reviews 
and other notices of the book and to change the phraseology 
or substance of the text wherever such modification, after 
careful consideration, seemed desirable, and when the 
modification could be made in conformity with the limit- 
ing conditions stated in the preface to the second edition 
It is hoped that the changes made better fit the book foi 
the purposes intended. 

West Point, N. Y., March 1, 1901. 



PREFACE TO FOURTH EDITION. 



In preparing for a reprint of this book advantage has been 
taken of the opportunity to bring all descriptive processes up to 
date as nearly as practicable. 

The order of sequence of chapters two and three, observed in 
former editions, has been changed and the contents of chapter 
three, as now numbered, much increased. In this enlarged 
chapter it has been attempted to present in concise form most of 
the more important generalizations in Chemistry that have been 
reached and which are of fundamental importance. Some of 
these generalizations are very recent but only such as are thought 
to stand upon a substantial basis are introduced. The preface 
to the second edition, which is still retained in this, gives the 
general purposes of the book and the conditions of its preparation. 
It is proper to here add that the time of the student now available 
for the study of the matter embraced is about one fourth greater 
than that stated in the second edition. 

S. E T. 

West Point, N. Y., July r, 1907 



TABLE OF CONTENTS. 



CHAPTER I. 

ESSENTIAL PRINCIPLES OF CHEMISTRY. 

PAGES 

itroductory remarks 1-3 

Table of elements 4 

Laws of fixed proportions and multiples 3-6 

Atomic theory 6-8 

Chemical notation and nomenclature 8-14 

Chemical reactions and conditions affecting affinity 14-20 

Radicals, bases, acids, and salts 20-27 

Equivalent and atomic weights 27-32 

Law of Avogadro and determination of molecular weights 32-36 

Atomic weights from Avogadro's law 36-39 

Number of atoms in molecules, isomorphous relations 39-43 

Volume relations of elements and compounds 43-45 

Relations between specific heat and atomic weights 45-48 

Valency 48-53 

Properties of certain important substances 53-54 

Stochiometry 54-58 



CHAPTER II. 

NON-METALS. 

Oxygen and ozone 59-65 

Hydrogen 65-70 

Nitrogen and atmospheric air 70-74 

Water and hydrogen peroxide 74-87 

Carbon and its different forms 87-95 

Compounds of carbon and oxygen 95-102 

Hydrocarbons (methane, acetylene, ethylene) 102-105 

Combustion and flame 105-116 

vii 



TABLE DF CONTENTS. 



Silicon and boron .- 116-119 

Compounds of hydrogen ai k d nitrogen 119-123 

Compounds of nitrogen and oxygen 123-129 

Chlorine and hydrochloric acid 129-136 

Bromine, iodine, and fluorine 136-140 

Sulphur 140-144 

Hydrogen sulphide ind oxides of sulphur 144-150 

Sulphuric acid and sulphates, other sulphur acids 150-160 

Selenium and tellurium 160-161 

Phosphorus, oxides, and oxy-acids of phosphorus 161-166 

Arsenic and its non-metallic compounds 166-168 

Argon and iielium ! 169 

CHAPTER III. 

ADDITIONAL GENERAL PRINCIPLES. 

Kinetic molecular theory 171-172 

Affinity : 172-173 

Influence of mass 173-178 

Solutions 178-181 

Osmotic pressure 181-184 

Dissociation by heat 184-186 

Dissociation by solutions 186-190 

Electrolysis 190-197 

Acids and bases 197-199 

Heat of neutralization 200 

Ionic conduction of electricity ^ 200-201 

Thermochemistry 201-206 

Periodic law 207-212 

Retroactive elements . 212-219 

CHAPTER TV. 

METALS. 

Potassium and its compounds 221-229 

Sodium and its compounds 229-237 

Ammonium and its compounds 237-240 

Barium and its compounds 240-242 

Calcium and its compounds 242-247 

Magnesium 248-249 

Zinc and its compounds 250-254 

Cadmium and beryllium 254-255 

Alluminum and its compounds 265-260 

Iron, its reduction, metallurgy, and important compounds 260-289 

Cobalt, nickel, manganese, chromium 289-291 



TABLE OF CONTENTS. ix 

PAGES 

Molybdenum, tungsten, uranium, bismuth, and antimony 292-293 

Tantalum, niobium, and vanadium 265-293 

Tin and its reduction . . . 293-296 

Titanium, zirconium, thorium, germanium, cerium ......... 296 

Lead, its reduction and important compounds . . . 296-307 

Copper, its reduction and important compounds 307-315 

Silver, its reduction and important compounds ............ 315-323 

Mercury, its reduction and important compounds 323-328 

Platinum and other metals of the same group 328-331 

Gold, its metallurgy and important compounds ................... 331-338 

CHAPTER V. 

ORGANIC CHEMISTRY. 

Chemistry of the carbon compounds 339-340 

Classification of carbon compounds 340-342 

Structural and rational formulae 342-343 

Isomerism and polymerism 343-344 

Saturated hydrocarbons 344-347 

Unsaturated hydrocarbons 347-348 

Acetylene series 348-349 

Benzene series 349 

Terpenes 349-351 

Camphors, resins, balsams 351 

Caoutchouc, india-rubber 351-355 

Gutta-percha 355 

Alcohols 355-362 

Acetic acid 362-365 

Acetates 365-366 

Vegetable acids 366-368 

Ethers 368-370 

Cyanogen and its compounds ........ 370-371 

Phenols 371-372 

Carbohydrates 372-386 

Vegetable colors 380 

Albuminous substances 381-383 

Alkaloids 383-384 

CHAPTER VI. 

APPLICATIONS OF CHEMISTRY. 

Calorific value 385-386 

Calorific intensity 386-388 

Glass-making 388 393 



X TABLE OF CONTENTS. 

PAGES 

Pottery manufacture 393-397 

Explosives . 397-413 

Manufacture of coal-gas 413-420 

Alcoholic beverages 420 

Beer making '. 421-423 

Wine making 423-425 

Distilled liquors 425-426 

Bread-making 426-429 

Fixed oils 429-431 

Manufacture of soap 431-433 

Manufacture of leather 433-437 

Preparation of cheese 437-438 

Dyeing. ... 438-439 



DESCRIPTIVE GENERAL CHEMISTRY, 



CHAPTER I. 
ESSENTIAL PRINCIPLES OF CHEMISTRY. 

The science of chemistry has for its object the study of 
the nature and properties of all kinds of homogeneous 
matter and endeavors to classify the changes which matter 
undergoes. Nearly all substances accessible to man are of 
a compound nature, and may be decomposed or separated 
into simpler forms of matter, these simpler forms being 
generally very different from the original substances ; 
thus, water is a compound substance and may be separated 
into its constituents, which are gaseous bodies, oxygen and 
hydrogen. Common salt is a compound, one of its con- 
stituents being a white-solid and the other a yellowish- 
colored gas. 

Those substances which thus far have not been sepa- 
rated into simpler forms of matter are called elementary 
substances or simply elements. The terms chemical af- 
finity, chemical attraction, and force of affinity have been 
used to designate that property of matter by virtue of 
which substances enter into combinations and form com- 
pounds. The compounds so formed generally have charac- 
teristics entirely different from those of their constituents. 

l 



H INTRODUCTORY OUTLINES. 

The force of affinity must be clearly distinguished from 
other forces exerted between all descriptions of matter, 
such as cohesion, which binds together the individual par- 
ticles of the same body, and adhesion, which designates 
the attraction existing between the particles of different 
bodies, as the adhesion of a liquid to glass ; other effects 
are also observed which come under the head of molecular 
actions. From all these, chemical attraction is distin- 
guished by the complete change of character which follows 
its action ; it might be defined as that property of matter 
by virtue of which new bodies are generated. This prop- 
erty of matter is concerned in all chemical changes, and 
chemistry may be defined as the science which investigates 
the relations which affinity establishes between bodies, 
considers its mode of action, attempts to determine the 
laws governing this action, and examines the character 
and constitution of the substances which result from its 
operation. Chemical changes permanently affect the prop- 
erties of bodies, and physical usually do not. 

There are at present generally recognized about seventy- 
eight elementary bodies, but this number is at any time 
liable to either increase or decrease by the discovery of a new 
body or the decomposition of one previously recognized as 
an element. Of the total number, fifty-eight are usually 
classed as metallic and the others as non-metallic. This divi- 
sion is in part arbitrary, since the divisions graduate into 
each other. The accompanying table classifies the elements 
as above stated, the most important being distinguished 
by heavier type and italics. 

Potassium and sodium are the important members of a 
group known as alkaline metals ; barium, calcium, and 
strontium of the alkaline ear^A-metals. It will be conve- 
nient for the student to remember these groups in addi- 
tion to the more common metals. 



ESSENTIAL PRINCIPLES. 



Elementary Bodies with their Symbols and Atomic Weights. 

Hydrogen taken as the standard for atomic weights. 

metals. 



Name. 



Aluminum . . . . 

Antimony 

Barium 

Beryllium 

Bismuth 

Cadmium 

Caesium 

Calcium 

Cerium 

Chromium . . . . 

Cobalt 

Copper 

Erbium 

Gadolinium . . . 

Gallium 

Germanium . . . 

Gold 

Indium 

Iridium 

Iron 

Lanthanum . . . 

Lead 

Lithium ... 
Magnesium. . . . 
Manganese 

Mercury 

Molybdenum . . 
Necdymium. . . . 
Nickel 

Argon 

Arsenic 

Boron 

Brom'ne 

Carbon 

Chlorine 

!'"lu~>rini 

Helium 

Hydrogen 

Iodine 



Symbol. 


Atomic 
Weight. 


Nearest 
Whole 
Number 


Al 


26.9 




Sb 


119.3 




Ba 


136.4 




Be 


9.0 




Bi 


206.9 




Cdv 


111.6 




Cs 


132 




Ca 


39.8 


40 


Ce 


139 




Cr 


51.7 




Co 


58.5 




Cu 


63.1 


63 


E 


164.8 




Gd 


155 




Ga 


69.5 




Ge 


71.9 




Au 


195.7 


196 


In 


113.1 




Ir 


191.5 




Fe 


55.5 


56 


La 


137.9 




Pb 


205.4 


205 


Li 


7 




Mg 


24.2 




Mn 


54.6 




Hg 


198.5 




Mo 


95.3 




Nd 


142.5 




Ni 


58.3 





Name. 



Niobium 

Osmium 

Palladium .... 

Pla inum 

Potassium. . . . 
Praseodymium 

Radium 

Rhodium .... 
Rubidium .... 
Ruthenium . . 
Samarium .... 
Scandium .... 

Silver 

Sodium 

Strontium .... 
Tantalum . . . . 

Terbium 

Thallium 

Thorium 

Thulium 

Tin 

Titanium . . . . 
Tungsten . . . . 

Uranium 

Vanadium. . . . 
Ytterbium . . . 

Yttrium 

Zinc 

Zirconium .... 



Symbol. 



Nb 

Os 

Pd 

Pt 

K 

Pr 

Ra 

Ro 

Rb 

Ru 

Sm 

Sc 

Ag 

Na 

Sr 

Ta 

Tb 

Tl 

Th 

Tm 

Sn 

Ti 

W 

U 

V 

Yb 

Yt 

Zn 

Zr 



Atomic 
Weight. 



93.3 
189.6 
105.7 
193.3 

38.9 
139.4 
223.3 
102.2 

84.8 
100.9 
148.9 

43.8 
107.1 

22.9 

87 

181.6 
158.8 
202.6 
230.8 
169.7 
118.1 

47.7 
182.6 
236.7 

50.8 
171.7 

88.3 

64.9 

89.9 



Nearest 
Whole 
Number 



39 



107 
23 



65 



etals. 

Krypton . . . 

Neon 

Nitrogen. . . 
Oxygen. . . . 
Phosphorus 
Selenium . . . 

Silicon 

Sulphur.. . . 
Tellurium . . 
Xenon 



A 


39.6 




As 


74.4 




B 


10.9 




Br 


79.4 




C 


11.9 


12 


CI 


35.2 


35 


F 


18.9 




He 


4 




H 


1 




I 


125.9 





Kr 


81.2 


Ne 


19.9 


N 


13.9 


O 


15.9 


P 


30.8 


Se 


78 . 6 


Si 


28 . 2 


S 


3 1 . 8 


Te 


126.0 


Xe 


127 



14 
16 
31 



32 



For facility in memorizing and convenience in computation the nearest 
whole numbers to the determined atomic weights of certain elements are 
given in column four of the table Thes j numbers will be generally em- 
ployed in the text in purely illustrative computations and should be memo- 
rized by the student. 



4 INTRODUCTORY OUTLINES. 

These substances present every variety of physical 
character, state of aggregation, etc. ; some are solid, some 
liquid, and some gaseous ; some are light, others heavy, 
some occur in the free state and others only in combina- 
tion. About sixteen elements make up ninety-nine hun- 
dredths of all known matter. 

It was in the last quarter of the 18th century that the 
conclusion was reached that matter could neither be 
created nor destroyed by human agency. To Lavoisier, 
the French chemist, belongs the great distinction of hav- 
ing first asserted the principle of the indestructibility of 
matter. This principle is now generally known as the 
Law of Conservation of Matter, and to it all physical and 
chemical deductions alike must conform. It is the most 
general law governing chemical processes, and as regards 
such processes, may be stated as follows : In chemical 
processes the mass of matter involved in any process is 
unchanged. 

LAW OF FIXED OR DEFINITE PROPORTION. 

The relative toeights of the constituent elements in any 
/Jiemical compound are fixed; or, the same compound al- 
ways contains the same elements in the same proportions 
by w eight. This was the first general law governing chem- 
ical constitution discovered ; it was recognized before but 
not fully established until the beginning of this century. 
Thus, in 100 pounds of water, which is a compound of oxy- 
gen and hydrogen, there are always 

88.889 pounds of oxygen 
and 11.111 pounds of hydrogen. 

In 100 grains of lime, which is a compound of calcium and 
oxygen, there are always 

28.571 grains of oxygen 
and 71.429 grains of calcium. 



ESSENTIAL PRINCIPLES. 5 

The same fixity of proportions exists among the constitu- 
ents of all compounds. 

It is the law of definite proportions which so clearly dis- 
tinguishes true chemical compounds from mere mechanical 
mixtures ; in the first, the constituents are always in fixed 
proportions, in the mixture they may be in any propor- 
tions ; in a mixture the ingredients may generally be dis- 
tinguished and separated by mechanical means alone, but 
such means are not alone sufficient to distinguish or sepa- 
rate the constituents of a chemical compound. Again, as 
has been stated, in a chemical compound the properties 
of the constituents have entirely disappeared, but in a 
mixture the properties of the ingredients exist in vary- 
ing degrees, depending upon the proportions of the in- 
gredients. 

SOLUTIONS AND ALLOYS. 

Although these distinctions characterize true chemical 
compounds and mechanical mixtures, there are classes of 
bodies such as solutions and alloys in which these distinc- 
tions do not so plainly exist. Bodies in these states appear 
to be in less intimate condition than true chemical union 
and more so than that of mechanical mixture. These 
bodies (solutions, alloys, etc.) graduate imperceptibly, on 
the one hand, into true chemical compounds, and on the 
other into mere mixtures. The laws governing the forma- 
tion of such bodies are not fully known. The word com- 
pound in the text is always used to indicate a true chemical 
compound, that is, one of which the proportions of the 
constituents are invariable and otherwise characterized as 
above stated. The supposed nature of solutions will be 
referred to more fully. 



INTRODUCTORY OUTLINES. 



LAW OF MULTIPLES. 



The same elements generally unite in more than one 
proportion, forming different compounds; in such cases the 
proportions between the same elements produce simple 
ratios. The law may be more specifically stated as follows : 
When two bodies A and B unite in several proportions the 
different quantities o/B, which unite with a fixed quantity 
of A, bear a simple ratio to each other; thus the several 
quantities of sulphur which unite with the same quantity 
of potassium are to each other as the numbers 1, 2, 3, 4, and 
5, and the same numbers give the different amounts of oxy- 
gen which unite with the same quantity of nitrogen, as 
illustrated in the following tables : 



)tassium. 

2.438 


Sulphur. 
1 


Nitrogen. 
1.75 


Oxygen, 
1 


2.438 


2 


1.75 


2 


2.438 


3 


1.75 


3 


2.438 


4 


1.75 


4 


2.438 


5 


1.75 


5 



This is the second general law governing chemical constitu- 
tion that was established. 

THE ATOMIC THEORY. 

The above law was discovered by Dalton of Manchester, 
and his writings show that he had observed it as early as 
1802. From his investigations during 1803 and 1804 he 
gained a clear conception of the law, and it is involved in 
the results at which he arrived, though it was not published 
until 1805. 

At about the same time, and largely by the consideration 
of the same data that established the Law of Multiples, 
Dalton was led to propose the Atomic Theory, which was 



ESSENTIAL PRINCIPLES. 7 

published in 1807. This theory asserts that all simple 
bodies are composed of small indivisible particles, or 
atoms, the atoms of any element having all the same 
weight, which is different from the weight of the atoms 
of all other elements, and chemical compounds always 
result from the combination of a definite number of atoms 
of different elements forming compound atoms. 

The law of definite proportions and the law of multiples 
are both reasonably explained by this theory ; in case of 
the first, it is only necessary to conceive that the compound 
atoms of a substance always contain the same number of 
atoms of each of its elements ; in the second case, more 
than one compound between two elements can result only 
by the successive additions of one or more entire atoms. 

, The above is the substance of Dalton' s Atomic Theory. 
In its essential points it has been strengthened by the sub- 
sequent test of experimental research, and in its expanded 
form is the basis of the developed chemistry of to-day. 
The atoms in Dalton' s theory were assumed to be indivis- 
ible, but the chemistry of to-day merely asserts that they 
have not been divided and not that they cannot be. The 
particles formed by the union of atoms, which Dalton 
designated compound atoms, correspond to what we now 
term molecules. 

The smallest particles of matter which in aggregate 
make up a body, and which are endowed with all and 
only the qualities and properties of the body itself, are 
now termed molecules. Molecules in general result from 
the combinations of atoms of the same or different kinds, 
but the molecules of some bodies appear to consist of a 
single atom. 

Those substances whose molecules consist of a single 
atom, or whose molecules result from the combination of 
atoms of the same kind, are elementary substances, or 



8 INTRODUCTORY OUTLINES. 

elements ; those substances whose molecules result from 
the union of atoms of different kinds, are compound sub- 
stances. 

If the molecules of a compound body are resolved into 
their constituents the properties of the body are always 
changed. It can scarcely be doubted that the disintegra- 
tion of the molecules of an elementary substance would 
affect the properties of the element; but the fact cannot be 
demonstrated as in the case of compounds. 

The atoms are the smallest individual masses of matter 
that have yet been found to enter bodies. They do not 
ordinarily exist separately, but as the constituents of mole- 
cules. The molecules can exist separately, and each has 
the precise properties of the body of which it forms a 
homogeneous part. 

Compound molecules themselves sometimes unite, form- 
ing molecules of still greater complexity, or molecules of 
the second order, or even higher orders. 



CHEMICAL NOTATION. 

Elements. The atomic theory is expressed, in the nota- 
tion employed in chemistry. The symbols of the elements 
are given in the second column of the preceding table. 
The symbols employed are the first letters of the Latin 
names of the elements, a second letter being added when 
the names of more than one element begin with the same 
letter. These symbols represent atoms of their respec- 
tive elements, the different atoms of different substances 
having different weights, as already stated. Several atoms 
of the same element are represented by placing a coefficient 
before the symbol or a numeral to the right and below, thus 
three atoms of hydrogen are represented by 

3H or H, . 



ESSENTIAL PRINCIPLES. 9 

Compounds. A molecule resulting from the combination 
of atoms of different kinds is represented by placing the 
symbols of the atoms in juxtaposition, thus a molecule of 
common salt, a compound of sodium and chlorine, is repre- 
sented by 

NaCL 

If more than one atom of either element enters the molecule 
it is shown by placing the corresponding numeral to the right 
and below the symbol of the element, thus a molecule of 
water is a compound of one atom of oxygen and two of 
hydrogen, and is represented by 

OH a . 

When it is desired to indicate several molecules, the 
numeral is placed as a coefficient or the molecule is enclosed 
in brackets and the numeral placed to the right, thus three 
molecules of water would be represented by 

30H, or (OH,),. 

A combination of molecules is sometimes indicated by their 
juxtaposition with a comma between, thus the combination 
of zinc oxide (ZnO) and sulphuric oxide (SO s ) may be indi- 
cated by 

ZnO, SO s ; 

to indicate a group of such molecules they are enclosed in 
brackets and a coefficient placed to the left, thus 

3 (ZnO, SO,). 

Combinations of molecules, however, are more generally 
indicated by grouping the symbols of the elements involved 
and placing the proper numerals to the right and below to 
show the number of atoms of each element which enter ; thus 
the compound above indicated would be written 

ZnS0 4 . 



10 INTRODUCTORY OUTLINES. 

A molecule of water (OH 2 ) combining with a molecule oi 
sulphuric oxide (SO,) would form a molecule represented by 

S0 4 H 2 . 

Again, CO a combining with OH 2 would give 

C0 3 H 2 . 

These molecules are multiplied by placing a coefficient iu 
front, as 

2ZnS0 4 , 3S0 4 H 2 , 5C0 3 H 2 , etc. 

NOMENCLATURE. 

The names of the elements correspond to no fixed rule. 
Some are named in allusion to a certain property, or to a cir- 
cumstance connected with their discovery or history. The 
names of the more recently discovered metals end in um and 
several of the more recent non-metals in ine, as sodium, 
potassium, platinum ; chlorine, bromine, etc. 

Binary Compounds. Compounds are termed binary, 
ternary, quaternary, etc., according as they contain two, 
three, or four elements. Binary compounds of metallic and 
non-metallic elements are usually named by changing the 
termination of the non-metallic element into ide ; thus, 
compounds of oxygen, chlorine, sulphur, etc. , with metals 
are called respectively oxides, chlorides, sulphides, etc., as 
potassium oxide, sodium chloride, lead sulphide. The 
same method of naming holds in binary compounds of non- 
metallic elements ; the termination of the more distinctly 
non-metallic element is changed into ide, thus a combination 
of S and forms a sulphur oxide, of H and CI a hydrogen 
chloride, of C and O a carbon oxide, etc. 

Oxides. The oxides are very numerous and important, and 
for convenience are divided into two principal classes. The 
first class contains all those oxides whose chemical properties 






ESSENTIAL PRINCIPLES. 11 

are similar to those of the oxides of K, Na, Pb, etc., and are 
called basic oxides. The second class contains all those 
oxides whose chemical properties are similar to the oxides of 
S, C, P, and 'N, etc., and are called acid oxides ; generally 
the oxides of the metals are basic and of the non-metals acid. 
Some of the acid and basic oxides are capable of uniting 
directly and forming compounds called salts, thus when the 
oxide of sulphur (SO,) in vapor is passed over heated 
barium oxide (BaO), combination ensues and a salt called 
barium sulphate (BaSOJ is formed. There is also an inter ^ 
mediate group of oxides designated as neutral oxides, be^ 
cause of their slight disposition to enter into combination ; 
manganese dioxide (MnO a ) is an example of this class. These 
neutral oxides may also be formed from non-metals ; water 
(H 9 0) and carbon monoxide (CO) are examples. These 
classes are not separated by distinct lines but graduate into 
each other; the same oxide may sometimes exhibit either 
acid or basic properties according to circumstances. Again, 
although the most characteristic basic oxides are oxides of 
the metals, yet many metallic oxides, especially among the 
higher oxides, exhibit acid properties. 

Oxy-acids. Most acid oxides unite readily with water, 
forming compounds called oxy-acids, which in aqueous 
solution possess the properties termed acid, such as sour 
taste, corrosive action, the power of reddening certain blue 
vegetable colors, and yet more important, the power of 
exchanging the hydrogen which they contain for a metal and 
forming salts. Thus the oxide of sulphur (SO,), called 
sulphuric oxide, unites energetically with water (OH,\ form- 
ing sulphuric acid, the formula for which is H,S0 4 . Again, 
the oxide of nitrogen (N a B ), called nitrogen pentoxide, will 
unite with water forming nitric acid (N a 6 H„) or 2HN0,. 
Carbon dioxide (CO,) also unites with water, forming 
(H a CO,) carbonic acid. Sulphuric or nitric acid will act upon 
zinc and exchange its hydrogen for the metal and form a salt 



12 INTRODUCTORY OUTLINES. 

called zinc sulphate or zinc nitrate. The property of 
exchanging their hydrogen for a metal is the most character- 
istic property of acids and will be referred to again. It is 
now seen that salts may be formed in two ways, either by 
the direct union of basic and acid oxides or by the replace- 
ment of the hydrogen in an acid by a metal. 

Prefixes. Binary compounds of oxygen following the 
law of multiples are distinguished as mono, di, tri, etc., ac- 
cording to the degree of oxidation; a compound intermediate 
between a monoxide and a dioxide is called a sesquioxide, as 

CrO, chromium monoxide ; 

CrO a , chromium dioxide ; 

Cr0 3 , chromium trioxide ; 

Cr a O s , chromium sesquioxide, etc. 

Binary compounds of the other elements under the 
same law are designated in the same way ; as, 

monosulphide, monochloride, 

disulphide, dichloride, 

etc. etc. 

Suffixes. When an element forms but two important 
oxides they are often named by placing before the word 
oxide the name of the element with the termination ous 
for the lower, and ic for the higher oxide ; thus, 

Sulphurous oxide, S0 2 ; 
Sulphur/c oxide, SO s . 

These same terminations are also used to specify the 
two more important oxides of an element even when it 
forms other important oxides ; thus, the basic salifiable 
(salt-forming) oxides of iron are 

FeO, ferrous oxide ; 

Fe 2 O s , ferric oxide. 



ESSENTIAL PRINCIPLES. 13 

The salts which are formed from such oxides have the 
same terminations, as ferrous and ferric salts. 

It has been stated that the acid oxides unite with 
water, forming oxy- acids, and that these acids may form 
compounds called salts, by exchanging their hydrogen for 
a metal. If the name of the oxide terminates in ous, or it 
is the lower of two important oxides, the name of the acid 
formed by its union with water will terminate in ous ; 
thus, 

Sulphurous oxide unites with water and forms sul- 
phurous acid ; 

Nitrogen trioxide unites with water and forms nitrous 
acid ; 

Phosphorous oxide unites with water and forms phos- 
phorous acid. 

The salts which result from these acids by exchanging 
their hydrogen for a metal, have the termination ite ; thus, 
salts from sulphurous acid are called sulphas, from ni- 
trous acid, nitrites ; as, lead sulphite, potassium nitrite, 
etc. If the oxide terminates in ic or is the higher of two 
important oxides, the acid formed by its union with water 
will also terminate in ic ; thus, 

Sulphuric oxide unites with water, forming sulphuric 
acid ; 

Phosphoric oxide unites with water, forming phos- 
phoric acid ; 

Carbon dioxide unites with water, forming carbonic 
acid, etc., etc. 

Mtrogen pent oxide unites with water, forming nitr/c 
acid; 

The salts which result from the oxy-acids ending in /c, by 
an exchange of hydrogen for a metal, have the termination 
ate; thus, salts from the last named acids are sulphates. 



14 INTRODUCTORY OUTLINES. 

nitrates, phosphates, respectively, as lead sulphate, potas- 
sium nitrate, etc. 

Hydracids. The acids above referred to are all oxy-acids, 
and it was once supposed that all acids contained oxygen. 
We now know that there are bodies possessing all the 
properties of acids which do not contain oxygen; they 
all, however, contain hydrogen, and are capable of ex- 
changing this hydrogen for a metal and forming salts. 
Some of the acids which contain no oxygen are composed 
of hydrogen and one other element. There are only a few 
such examples. Some of them are, hydrochloric acid (HC1), 
hydrobromic acid (HBr), hydrofluoric acid (HF), sul- 
phydric acid (SH a ). The salts formed by replacing the 
hydrogen in the hydracids by a metal are named in accord- 
ance with the rule for binary compounds. Thus, when 
the hydrogen in hydrochloric acid is replaced by zinc, we 
have zinc chloride ; if potassium replace the hydrogen in 
hydrobromic acid, we have potassium bromide, etc. 

The above system of nomenclature is the one most gen- 
erally followed, but there are slight departures from it by 
certain chemists,- and there are still other terms to be de- 
fined. The principle of the system is that the composition 
of the compound shall be briefly expressed in its name. 
In addition to this, many substances have popular names, 
which will be found in the text, or have been otherwise 
named, as will be subsequently explained. 

CHEMICAL REACTIONS. 

Chemical changes in bodies, whether brought about by 
the reciprocal action of chemical agents upon each other, 
or by the influence of other agents, are called reactions. 
From the definition of molecules it is evident that these 
changes take place among the molecules, and although 
these molecules are invisible, it should be appreciated that 



ESSENTIAL PPdNCIPLES. 15 

whatever chemical changes occur in the bodies must come 
through an alteration of their molecules. By means of 
the symbols given we can represent the changes which are 
known to occur. Reactions are usually represented by 
equations, in the first member of which are placed the 
formulae of the substances employed, called reagents, and 
in the second member the formulae of the products ob- 
tained. Reactions, in so far as they are represented by 
equations, consist either in the direct addition or separa- 
tion of elements, or in the substitution of an atom of one 
element for one or more atoms of another element, or of a 
group of atoms of one molecule for a similar group of 
another. 

We thus have first, synthetical reactions in which a 
more complex body is formed by the union of simpler 
bodies. In such cases those substances which differ most 
in chemical properties act most readily upon each other ; 
thus, 

BaO + SO, = BaS0 4 Pb + O = PbO. 

Second, analytical reactions, as when calcium carbon- 
ate is heated it yields calcium oxide and carbon dioxide ; 
thus, 

CaCO, heated = CaO + CO,. 

In this class a more complex body is separated into simp]er 
ones. 

Third, metathetical reactions, in which the transforma- 
tion of previously existing compounds is brought about 
either by simple substitution or double decomposition ; 
thus, 

Zn + 2HC1 = ZnCl, + H 2 . 

JSTaCl + AgNO, = AgCl + NaNO,. 

In the case of double decomposition, if the body desired 



16 INTRODUCTORY OUTLINES. 

be a salt, one of the reagents mnst contain the acid part 
and the other the basic part of the salt desired. 

These equations are but the expressions of observed 
facts, and their truth is known from observation, and not 
from deduction. They express only the known results 
from known premises and give no indication of the com- 
plex phenomena which the reaction often involves. They 
represent merely the distribution of weights before and 
after chemical change. In every reaction, since there is 
only a change, and not a loss or destruction of matter, the 
total weights of matter in the two members must be the 
same, as also must be the total number of atoms of each 
and all the elements. The chemical meaning of the re- 
action-equation should not be obscured by the algebraic 
symbols employed. Thus, in the equation above, Zn + 
2HC1 = ZnCl 2 + H 2 , the proper reading would be zinc 
acted upon by hydrochloric acid yields zinc chloride and 
hydrogen. The algebraic symbols are adopted for con- 
venience ancl have not at all their common significance. 
Some substances occur native, but the majority of them 
are obtained by one or the other of the above methods. 
The most common reactions are of the metathetical kind. 

DETERMINING CAUSES IN REACTIONS. 

Chemical affinity has been termed the property of mat- 
ter by which bodies are formed and exist as compounds. 
It is frequently conceived to be the cause of chemical 
action, and hence, termed the force of affinity. It is essen- 
tially concerned with action between atoms, but also ex- 
tends to action between molecules. Without limiting the 
conception of affinity it is convenient to adhere to the prac- 
tice of designating it as a force. Chemical affinity operates 
in all kinds of reactions. Only a complete knowledge of 
the laws of chemical action would enable the results of 
reactions to be predicted. 



ESSENTIAL PRINCIPLES. 17 

Reference will be made later to certain important cir- 
cumstances which, influence chemical action. Here we 
shall state a few conditions which determine the course of 
many common reactions and with which it is desirable that 
the student should early become familiar. 

Heat and Change of Temperature. Reactions are induced 
by changing the conditions to which substances are sub- 
jected, and the most important physical change is that of 
temperature. Many reactions are thus produced by changes 
of temperature. At one temperature mercury unites with 
oxygen, at another it separates from it. Many bodies are 
resolved into their constituents by heat. 

Solution. A great variety of chemical changes are in- 
duced by bringing substances into contact with each other. 
The force of affinity acts only at insensible distances, and 
whatever tends to prevent the closest proximity of the 
molecules tends to prevent action. Cohesion, in solids, 
evidently prevents such contact ; it is most perfect between 
two gases or two miscible liquids. Besides the fact that 
many bodies cannot be converted into gas, the liquid state 
is much more convenient. It is, therefore, very common to 
bring one or both of the reagents into a state of solution. 

Insolubility. It is a rule, almost without exception, that 
when two substances containing the constituents of an in- 
soluble or sparingly soluble one are brought together in 
solution, a reaction occurs, and the less soluble substance 
is formed. This rule may be illustrated by bringing to- 
gether in solution ammonium carbonate and calcium chlo- 
ride, when calcium carbonate, an insoluble body, will be 
formed, as indicated by the equation : 

(NH 4 ) 2 C0 3 + CaCl, = CaCO s + 2NH 4 C1. 

(Ammonium carbonate.) (Ammonium chloride.) 

An insoluble body, the product from a reaction of sub- 
stances in solution, is called a precipitate, and the body is 



18 INTRODUCTORY OUTLINES. 

said to be precipitated. This rule requires that the pre- 
cipitate shall be insoluble in the solution after the reaction 
has occurred. 

Volatility. When two substances containing the con- 
stituents of a volatile one are heated together, the volatile 
one is produced and driven off. This is illustrated when 
calcium carbonate and ammonium chloride are heated to- 
gether, ammonium carbonate is formed and volatilized : 

CaC0 3 + 21N"H 4 C1 (heated) = CaCl 2 + (NH 4 ) 2 C0 3 . 
Again, certain acids or acid oxides which are volatile may 
be displaced by others less volatile. 

The reactions conditioned by insolubility and volatility 
are numerous and constitute many of those most frequently 
met with. They often take place independently of the 
order or strength of affinity of the reacting substances as 
determined by other comparisons. These rules are very 
important in forecasting or explaining the results of reac- 
tions. 

Physical Surroundings. If the vapor of water be 
passed over heated iron filings it is decomposed and iron 
oxide is formed ; on the other hand, if hydrogen gas be 
passed over heated iron oxide it reduces it to the metallic 
state while the vapor of water is reformed: 

3Fe + 40H 2 = Fe 3 4 + H 8< 



^^. v^ , -^v^-^-jj -^ ^3^4 I -*-"-8» 

H 8 + Fe 3 4 = 3Fe + 40H a . 



Again, if sulphydric acid gas in excess be passed over acid potassium 
carbonate, slightly heated, carbon dioxide is liberated and potassium sul- 
phide formed, whereas, if carbon dioxide is passed through a solution of 
potassium sulphide the acid carbonate is reformed and sulphydric acid gas 
passes off. 

Nascent State. Many elements are more active at the 
moment of liberation from compounds than at other times. 
This active state of a newly -liberated body is called the 
nascent state. It is very favorable to chemical action. 



ESSENTIAL PRINCIPLES, 19 

Ordinarily if we force hydrogen through nitric acid no ac- 
tion occurs, but if the hydrogen be generated in the acid, 
by putting in a piece of zinc, the nascent hydrogen will 
decompose some of the acid. 

Catalytic Action. This refers to effects which are ap- 
parently brought about by the mere presence of a body. 
Thus, if potassium chlorate be heated with manganese di- 
oxide it is decomposed more easily than when heated alone. 
The same effect is produced by the presence of certain other 
oxides, and is probably due to the fact that these oxides 
pass to a state of higher oxidation and then in turn are 
themselves reduced. Only oxides capable of higher oxida- 
tion produce this result. Catalytic action is also observed 
in solutions. Slow reactions, in solutions, are generally 
hastened by the presence of acids. 

Disposing Affinity. This term is used to embrace an 
extensive class of actions which are induced by the pres- 
ence of certain bodies and which would not occur in their 
absence. It differs from the catalytic action in that the 
disposing body is found to be changed at the close of the 
operation, while the influencing body in catalysis is not. 

It should be understood that these so-called cases of 
modified chemical action are only the statements of facts 
invariably observed. These facts will soon undoubtedly be 
included under the more perfectly developed laws govern- 
ing chemical action. Many examples of this action will be 
observed as progress is made in the course. 

Influence of Pressure on Chemical Action. When a body 
is decomposed, in a confined space, by heat, some of the 
products being gaseous, the decomposition will go on 
until the liberated gas or vapor has attained a certain pres- 
sure, greater or less according to the temperature. No 
further decomposition will then take place, nor will the ele- 
ments or constituent gases recombine so long as the tem- 
perature remains fixed ; but if the temperature be raised, 



20 INTRODUCTORY OUTLINES. 

the decomposition will begin again and continue until the 
vapor reaches a tension definite for that temperature, when 
it will again cease. If, on the other hand, the temperature 
is lowered, recombination ensues until the tension of the 
remaining gases is reduced to that corresponding to the 
lower temperature. Decomposition under these conditions 
has been designated by Deville by the term "Dissocia- 
tion." 

The effect of pressure is also seen in the retarding influence it exerts 
in the action of acids upon zinc. If the escape of the gas which is liberated 
is prevented, the action is retarded. On the other hand, there are numer- 
ous reactions which are greatly promoted by increased pressure, such as 
those which depend on the solution of gases in liquids, or on the prolonged 
contact of substances which under ordinary circumstances would be vola- 
tilized by heat. 

RADICALS, BASES, ACIDS, AND SALTS. 

We are now prepared to supplement the system of no- 
menclature given, to a certain extent, and to explain the use 
of certain terms which have long been and still are in use 
in chemistry, and to more fully define others which we 
have already used. 

Radicals. In the metathetical reactions it was- indicated 
that the elementary atoms not only change places with each 
other, atom for atom, but one atom with more than one of 
another kind, or one with a group of other kinds or groups 
of atoms of different kinds with each other. These inter- 
changing atoms or groups appear to bear the same relations 
to the molecules they enter as did the atom or atoms re- 
placed. Thus, in the following reactions, 

AgN0 3 + NaCl = AgCl + NaNO, , 
AgNO, + JSTH 4 C1 - NH 4 BTO, + AgCl, 

the atom of silver is replaced in the first by an atom of so- 
dium, in the second by the group (NH 4 ), ammonium. Such 



ESSENTIAL PRINCIPLES. 21 

groups of atoms are called compound radicals, and it is 
assumed that in ordinary reactions they are transferred 
from molecule to molecule without loss of integrity. The 
elementary atoms which perform similar parts in different 
molecules may be called elementary radicals, so that the 
term radical is applied to both elementary atoms and 
groups of atoms. Only a few of the compound radicals 
have been isolated. They are assumed to so exist because 
the same group, or, at least, the same proportional amounts 
of the same elements, enter several compounds. The sym- 
bol of every compound molecule may be formulated into 
possible radicals, but unless the radicals enter several com- 
pounds there is nothing gained by the assumption. Radi- 
cals are designated as acid or basic according as they ful- 
fill the parts of acid or basic compounds. Of elementary 
radicals, generally the metallic atoms are basic, and the 
non-metallic atoms, acid radicals. Thus, in NaCl, the so- 
dium is the basic and the chlorine the acid radical. In ter- 
nary combinations the compounds of oxygen with the 
•metals are usually basic radicals, and the compounds of 
oxygen with the non-metals acid radicals. Thus, in 
BaO,S0 3 , the molecule BaO is basic, the other the acid 
radical ; in Na 2 S0 4 , the JN"a 2 is the basic, and the S0 4 the acid 
radical. Compound radicals consisting of carbon and hy- 
drogen only are usually basic, but those which contain oxy- 
gen also, are generally acid. The radical NH 4 is strongly 
basic. The basic radicals are also called electro-positive, 
and the acid electro-negative radicals. 

Base. This term is more general than basic oxide, 
already mentioned, and includes a class of bodies often 
designated basic hydrates, but better basic hydroxides. 
These hydroxides were formerly supposed to contain water 
in combination with a metal, but it is now pretty con- 
clusively shown that they contain oxygen and hydrogen 
in the form of hydroxyl (OH), and not in the form of water 
(OH,). 



22 INTRODUCTORY OUTLINES. 

Certain of the basic hydroxides can be formed by acting 
upon water with a metal or metallic oxide. This is the case 
with the hydroxides of the so-called alkaline and alkaline- 
earth metals. Of the first class, the most important are 
potassium and sodium. The formation of their hydroxides 
may be indicated as follows : 

2H 2 + K 2 = 2KOH + H 9 . 
H 2 + K 2 = 2KOH. 
2H 2 + Na, =2JSTaOH + H a . 
H 2 + JNa 2 = 2NaOH. 

These hydroxides, and those of the other alkaline metals, 
are readily soluble in water, give solutions which corrode 
the skin, and convert fats into soaps ; they differ from the 
hydroxides of all other metals (except that of barium) in 
that they are not decomposable by heat alone. 

Very similar in chemical properties to these hydroxides 
is that of ammonium, formed by dissolving ammonia gas 
(NH 3 ) in water. The great similarity of ammonium hy- 
droxide to the others named gives ground for the assump- 
tion that the radical ammonium, NH 4 , exists, and that 

ammonium hydroxide may be formulated.. NH 4 OH, 
just as potassium hydroxide is KOH. 

The hydroxides of the alkaline metals and of ammonia are 
often termed alkalies. 

The most important hydroxides of the alkaline-earth 
metals are those of barium and calcium. These hydroxides 
are only slightly soluble, and are less caustic than the 
alkalies. They can be formed in the same manner as the 
alkaline hydroxides, by acting upon water with a metal or 
metallic oxide. 

Ca + 2H 2 = Ca0 2 H 2 + H a . 

BaO + OH 2 = BaO a H 2 . 

Calcium hydroxide is decomposed by heat into calcium 






ESSENTIAL PRINCIPLES. 23 

oxide and water ; barium hydroxide is not decomposed by 
heat. 

All other metallic hydroxides are insoluble and are 
decomposed by heat, and cannot be formed in the manner 
above described. They may be obtained by bringing to- 
gether in solution one of the soluble hydroxides, and a salt 
of the metal whose hydroxide is desired ; thus, 

ZnCl 2 + 2KOH = 2KC1 + Zn0 2 H 2 . 

In this reaction the principle of insolubility comes into play 
and the insoluble hydroxide is precipitated. All the 
insoluble hydroxides are decomposed by heat into the cor- 
responding oxides and water, in general, at a moderate 
temperature. 

Metallic Oxides or Basic Anhydrides. The oxides of the 
metals or the basic oxides previously defined may be con- 
sidered as formed by replacing all the hydrogen in one or 
more molecules of water by the metal instead of a part, as 
in the formation of the hydroxides, K 2 -f- H 2 = K 2 4- H 2 . 
It has been stated above that many of the metallic hy- 
droxides are separated by heat into the corresponding 
oxides and water. The oxides may, therefore, be regarded 
as anhydrides of the hydroxides, and they are accordingly 
sometimes called basic anhydrides. 

The term base in inorganic chemistry is by some chem- 
ists applied only to the metallic hydroxides ; by others, it is 
extended also to basic oxides and to certain compound 
radicals, all of which form salts with acids. The former 
application has certain advantages ; the latter is, however, 
very common. 

Acids. The general properties of acids have already been 
stated, the most characteristic of which is their capacity to 
excliange a part or the whole of the hydrogen which they 
contain for metallic elements or basic radicals. Some of 
the acids contain only hydrogen and one other element, as 



24 INTRODUCTORY OUTLINES. 

hydrochloric acid (HC1), hydrobromic acid (HBr), sulphy- 
dric acid (SH 2 ), etc. ; but most acids consist of hydrogen 
and more than one other element, as H 2 S0 o sulphuric acid ; 
KN0 3 , nitric acid ; C0 3 H 2 , carbonic acid, etc. 

The hydrogen in all these acids may be replaced in 
several ways ; to wit, by acting on the acid with either a 
metal, metallic oxide, hydroxide, or a metallic salt ; thus, 

H 2 S0 4 + Na 2 = Na 2 S0 4 + H,. 
2HC1 + ZnO = ZnCl 2 + OH 3 . 
HBr + KOH = KBr + OH 2 . 
Ca0 2 H, + H 2 S0 4 = S0 4 Ca + 20H 3 . 
JSTH 4 OH + JTO 3 H = NH 4 N0 3 + OH 3 . 
HC1 + AgN0 3 = AgCl + HN0 3 . 

It is thus seen that although salts are sometimes formed by 
the direct union of a basic and an acid oxide (see page 11), 
they are far more generally formed by the replacement 
of the hydrogen in an acid, in part or whole, by a basic 
radical, either elementary or compound. 

The acids without oxygen are called hydrogen acids, or 
liydracids, and those containing it, oxygen acids or oxy- 
acids. The oxy-acids in general result from the action of 
acid oxides upon water ; as, 

S0 3 + H a O - H 2 S0 4 . JST,0 B + H a O = 2NO.H. 

It has now been very conclusively shown that in many 
cases these acids are compounds of hydroxyl with an acid 
radical, and that when the acid oxides combine with water 
the resulting acids contain one or more groups of hydroxyl 
(OH). The formulae of these acids may then with propriety 
be written to indicate the presence of the hydroxyl group ; 
thus, the formulae of the acids above given would be 
written SO a (OH) f , N0 3 (OH). 

Acid Anhydrides. The application of the term acid oxide has been 
already given (page 11). Many of these oxides can be obtained 1 3 



ESSENTIAL PRINCIPLES. 25 

abstracting the constituents of water from acids, and hence have also re- 
ceived the names of acid anhydrides, or simply anhydrides. 

As has been stated, most of these anhydrides display great readiness 
to unite with water, forming acids ; thus, 

S0 3 + H 2 = H 2 S0 4 . 

From the above considerations it is seen that the acid anhydrides bear the 
same relation to acids that the basic anhydrides bear to the hydroxides. 

Basicity of Acids. When an acid contains bnt one atom 
of hydrogen in its molecule replaceable by a metal or basic 
radical it is said to be monobasic ; when two, bibasic ; when 
three, tribasic ; etc. The basicity of an acid is fixed by 
the number of hydrogen atoms replaceable. In oxy-acids 
this number is in general believed to be the same as the 
number of hydroxyl groups. 

Monobasic acids can form but one class of salts, the 
metal replacing the whole of the hydrogen in one or more 
molecules of the acid. Thus, 

HC1 + K = KC1 + H ; 
2HCl + Zn = ZnCl 2 + H a . 

A bibasic acid may form two classes of salts, viz., 
primary or acid salts, in which only half the hydrogen in 
the molecule is replaced, and secondary salts, in which the 
whole is replaced ; in the latter case if tlie hydrogen is 
replaced by one metal the salt is called normal, and if by 
two metals double. Thus, 

KHS0 4 is an acid salt, acid potassium sulphate. 
K 3 S0 4 is a normal salt, normal " 
KNaS0 4 is a double salt, potassio-sodic " 

Tribasic acids may form three classes of salts ; primary, 
secondary, or tertiary, including normal, double, and triple, 
in which the hydrogen is wholly or partially replaced by 
one or more metals. The following list contains the most 



26 INTRODUCTORY OUTLINES. 

important and common inorganic acids, arranged according 
to basicity : 



Monobasic Acids. 


Bibasic Acids. 


Tribasic Acids. 


Hydrochloric, 


HC1. 


Hydric (water) OH a . 


Orthopbospboric, 


Hydrobromic, 


HBr. 


Sulphydric, SH 3 . 


H.PO*. 


Hydriodic, 


HI. 


Sulphuric, H 2 S0 4 . 




Hydrofluoric, 


HF. 


Carbonic, C0 3 H 2 . 


. 


Nitrous, 


HN0 2 . 


Pyrosulphuric, H2S3O7. 




Nitric, 


HN0 3 . 






Chloric, 


HC10 S 







Salts. The formation of salts by the direct union of acid 
and basic oxides, and by the replacement of the hydrogen 
in an acid, by different methods, has been already referred 
to. Now it is evident that in the reaction between acids 
and hydroxides, while we considered that the hydrogen of 
the acid was replaced by a metallic atom or basic radical, 
we might, with equal propriety, have considered the hy- 
drogen of the hydroxide as replaced by an acid radical, 
thus : in the indicated reaction, 

KOH + JN"0 2 OH = KNO, +H 9 0, 

we may consider the salt, KN0 3 , as formed either by the 
NO a of the acid replacing H of the hydroxide, or by K 
of the hydroxide replacing H of the acid. 

From these considerations it is evident that the term 
salt is a descriptive one and cannot be defined in indepen- 
dent language. 

If only a part of the hydrogen in the hydroxide be 
replaced by the acid radical the salt is called basic. Basic 
salts are also defined as those formed by the union of a 
normal salt with a basic oxide or hydroxide, the base thus 
being in excess of that necessary to form a normal salt. 
On the other hand, a normal salt may combine with an 
acid oxide so that there is an excess of acid oxide over 



ESSENTIAL FBIJVCIPLES. 27 

that necessary to form a normal salt. Such a salt is called 
an anhydro salt. 

EQUIVALENT WEIGHTS OR EQUIVALENTS. 

It has already been stated that substances may replace 
each other in combination, and that chemical actions gen- 
erally consist of an interchange between the elements of 
different molecules. When HC1 acts upon Zn, the zinc 
replaces the hydrogen, which is evolved as a gas ; when 
potassium is thrown upon water it replaces the hydrogen 
of the water forming KOH ; if mercury be added to a 
solution of silver nitrate the silver is replaced by the 
mercury and itself deposited. 

The relative quantities of the elements which thus 
replace each other in compounds were called equivalent 
weights or chemical equivalents. The equivalent weights 
of the elements were supposed to possess the same chemical 
value and to be capable of filling each other' s places directly 
or indirectly. It was attempted to make the equivalents 
definite and specific by defining them as those weights 
which combine with, or displace, or are chemically equiv- 
alent to one part by weight of hydrogen. 

Strictly speaking, quantities of elements could only be 
said to be equivalent when they had actually replaced 
each other in combination, but quantities of elements 
which are equivalent to the same quantity of another 
element are assumed to be equivalent to each other ; thus. 
35.5 parts of chlorine are known to unite with 1 part of 
hydrogen, 23 of sodium, and 108 of silver, consequently the 
numbers 1, 23, and 108 are the equivalent weights of hydro- 
gen, sodium, and silver. In a similar way the equivalents 
of all elements may be expressed. 

Equivalents thus considered are the result of direct 
experiment and are based on no hypothesis as regards the 



28 INTRODUCTORY OUTLINES. 

constitution of matter. But in addition to the fact that 
many of the equivalent weights have to be determined 
indirectly, there is another difficulty which arises as soon 
as we consider those bodies which combine in more than 
one proportion; thus, tin forms two chlorides, in one of 
which 59.4 parts of the metal are combined with 35.5 parts 
of chlorine, and in the other 29.7 parts of tin are combined 
with the same amount of chlorine. Which of these is to be 
taken as the equivalent weight of tin ? The same difficulty 
is encountered in all cases in which combination occurs in 
more than one proportion between two elements. This 
difficulty is still further increased when the indirect deter- 
mination of the equivalents are made by the comparison of 
several compounds of one element with two or more dif- 
ferent elements. The idea of equivalent weights is, there- 
fore, not definite. 

ATOMIC WEIGHTS. 

The distinction between atoms and molecules has 
already been given, and although the atom is the smallest 
mass of matter yet distinguished, the modern chemistry 
does not assert that the atom is beyond the limit of divisi- 
bility ; it simply asserts that it has not yet been divided, 
and that in all known chemical processes the atomic masses 
act as units, and it matters not what may yet be accom- 
plished in dividing atoms, their integrity is retained in all 
reactions with which we are at present familiar. 

With the promulgation of the atomic theory the deter- 
mination of the relative weights of the elementary masses 
or their relative combining numbers became an absorbing 
problem. These weights are the numerical constants of 
the science of Chemistry ; they are the essential data in all 
quantitative analysis as well as in the application of 
Chemistry to the necessities of daily life.* To make possi- 

* It is really the mass of the atoms that is here concerned, but the term 



ESSENTIAL PRINCIPLES. 29 

ble a clear understanding of the method of determining 
atomic weights the student must bear in mind that although 
we cannot isolate and operate upon a single molecule of a 
body, yet in transforming a body we but transform its 
individual molecules, and whatever change the body 
undergoes is also undergone by each molecule thereof, and 
whatever relation is found to exist among the constituents 
of a body also exists among the constituents of a single 
molecule. 

Determination of Atomic Weights by Analysis. By accurate 
analysis we can determine the proportions of the elements 
which enter many compounds and consequently the pro- 
portions of the elements which enter the molecules, and if 
we knew the number of atoms of each element in the mole- 
cule we could deduce the relative weights of the atoms. 

Thus the analysis of water shows that oxygen and 
hydrogen enter the molecule in the proportion by weight 
of oxygen = 8 and hydrogen = 1. If there were an equal 
number of atoms of each element in the molecule the 
numbers 8 and 1 would represent the atomic weights. 
Now there is another compound of oxygen and hydrogen 
in which the proportions by weight are oxygen = 16 and 
hydrogen = 1. Assuming from the first compound that 
the atomic weights are 8 and 1 we might in the second 
case conclude that the compound contained two atoms of 
oxygen ; this would then account for the new proportion 
16 to 1 ; but if we, with equal propriety, assume that the 
second compound contains one atom of each of the elements, 
then the relative atomic weights are 16 and 1 and the first 
compound, water, necessarily contains two atoms of 
hydrogen. 

Thus with nothing before us except the results of 

weight is now so generally employed in chemical literature that it will be 
retained ; it should, however, be remembered that the masses are the constants, 
the weights vary with locality. 



30 INTRODUCTORY OUTLINES. 

simple analysis, the atomic weights would be uncertain, 
they might be correct or they might be multiples or sub- 
multiples of the correct ones, depending upon whether or 
not the number of atoms which enter the molecule was 
correctly assumed. It will be seen that the above method 
can be supplemented and some information gained as to 
the number of atoms in a molecule by the method which 
next follows. 

Determination of Atomic Weights by Substitution. The 
method of substituting one element for another can often 
be made use of to assist in reaching a correct conclusion as 
to the number of atoms which enter the molecule. 

For example, if water be treated with metallic sodium 
it is acted upon in such a way as to produce a substance 
whose composition is 

Sodium, Hydrogen, Oxygen ; 
23 1 16 

and if this compound be evaporated to dryness and heated 
with more sodium the remaining portion of the hydrogen 
is driven out and replaced by the sodium and we have a 
compound of 

Sodium, Sodium, and Oxygen. 
23 23 16 

It is thus evident that the hydrogen in the molecule of 
water has been replaced by halves, and it follows from the 
conception of atoms that there must have been at least two 
atoms in the molecule. Now if we could be certain that 
the molecule contained only one atom of oxygen we would 
again have the atomic weights of hydrogen and oxygen to 
be 1 and 16. With only the data yet before us we could 
not certainly conclude that the molecule of water has but 
one atom of oxygen, and hence the atomic weights would 
still be uncertain. 



ESSENTIAL PRINCIPLES. 31 

Again, if we take marsh-gas, a compound of carbon 
and hydrogen, the hydrogen may be replaced by four 
separate substitutions, so that there must be at least four 
atoms of hydrogen in the molecule of marsh-gas ; and if it 
be assumed that they are combined with one atom of carbon 
we arrive directly at the atomic weights. But, as in the 
preceding case, the number of atoms of each element is not 
determined by substitution alone and the atomic weights 
would remain uncertain. 

Determination of Atomic Weights by Decomposition. By 
the decomposition of certain bodies and the formation of 
others it is sometimes possible to compare the amounts of 
a certain element in the two, and if the number of atoms of 
the element in either be known the number in the other is 
also determined. 

The above are the only purely chemical means for the 
determination of atomic weights, and it is seen that they 
leave a doubt as to the correct numbers. It should be 
borne in mind that by a combination of all the methods 
and by an examination and comparison of various com- 
pounds of the same element, the uncertainty is very small. 
Thus, in the case of carbon it is indisputable that the 
smallest increment or decrement which can be made in any 
compound is twelve times as great as the smallest weight 
of hydrogen that can be introduced or displaced, and if we 
adhere to the smallest separable portion as the atom, the 
uncertainty as to the atomic weight is exceedingly slight 
in the case of this and many other elements. 

These purely chemical methods for the determination 
of atomic weights have been supplemented by means de- 
pendent upon physical considerations. The coincidences 
between the results obtained by these different means are 
so satisfactory as to dispel doubt as to the correct atomic 
weights of the great majority of the elements, except such 
doubt as is due to imperfection of process. We will now 



32 INTRODUCTORY OUTLINES. 

explain the method of determining the atomic weight by 
the introduction of physical considerations. 



PHYSICAL AND CHEMICAL RELATION OF ATOMIC 
WEIGHTS. 

Law of Avogadro. From a consideration of the relations 
existing between the specific gravities and the determined 
atomic weights of certain elements, Avogadro, an Italian, 
in 1811 was led to propose the hypothesis that equal vol- 
umes of all gases under like conditions of temperature 

and pressure contain the same number of molecules. 

The hypothesis uses the word molecule in the sense already given, and 
involves the idea that the elements in their internal structures are anal- 
ogous to compounds, and that the molecules of elementary bodies may 
contain more than one atom, and it will later appear that there are good 
reasons for such belief. This hypothesis has become of fundamental 
importance in chemistry in determining molecular weights and settling 
atomic weights ; it is supported by the results of all investigations made 
to determine the internal structure of gases, and upon the theory of 
molecular mechanics it affords a mathematical explanation of the laws of 
compression and temperature, and if the mechanical theory of gases be 
accepted, the hypothesis of Avogadro follows as a mathematical neces- 
sity. From these considerations the hypothesis is to-day justly considered 
a law. 

Accepting Avogadro' s hypothesis as a natural law, it, 
of course, follows that the v nit volumes of gases under like 
conditions of temperature and pressure contain the same number 
of molecules; hence we have the following important coral- 
lary: The actual weights of molecules of substances are to each other 
as the actual weights of unit volumes of substances in the gaseous 
state under like conditions of temperature and pressure, or the 
molecular iveights of substances are directly proportional to their 
specif c gravities in the gaseous state. 

Determination of Molecular Weights. It is therefore plain 



ESSENTIAL PRINCIPLES. 33 

that the weights of the molecules of different gases may be 
readily obtained in terms of the weight of the molecule of 
any gas assumed as a standard by simply determining their 
specific gravities, with reference to the standard gas. It 
simplifies the comprehension of the subject here considered 
to adopt hydrogen as the standard for specific gravities. 

To illustrate the above method, let us suppose that a 
volume of oxygen weighs sixteen times as much as an 
equal volume of hydrogen, then since these volumes con- 
tain the same number of molecules the molecule of oxygen 
will weigh sixteen times as much as the molecule of hydro- 
gen ; or if a given volume of hydrochloric acid gas weighs 
18 times as much as an equal volume of hydrogen, the 
molecule of HC1 will weigh 18 times as much as the mole- 
cule of H. 

Now if we also take the weight of the hydrogen molecule 
as the standard for molecular weights, the molecular weights 
and specific gravities will be represented by the same num- 
bers ; thus, the specific gravity of oxygen referred to 
hydrogen is 16, the molecule of oxygen weighs 16 times as 
much as the molecule of hydrogen, and if the weight of the 
hydrogen molecule be taken as unity, the weight of the 
oxygen molecule is 16 ; therefore, when hydrogen is used 
as the standard for specific gravities and the weight of the 
hydrogen molecule as the standard for molecular weights, 
the molecular weights and specific gravities are indicated 
by the same numbers. 

If we should use half the weight of the hydrogen mole- 
cule as the standard for molecular weights, it is evident 
that the molecular weights would all be double what they 
were when we used the whole weight of the molecule as 
the standard, and then, instead of being indicated by the 
same numbers as specific gravities, the molecular weights 
would be the doubles of the specific gravities. For reasons 
which will appear subsequently, it is found convenient to 



34 INTRODUCTORY OUTLINES. 

use the weight of half of the hydrogen molecule as the 
standard for molecular weights. 

For' convenience we shall, following Prof. Cooke, call 
the weight of the half -hydrogen molecule a microcrith, and 
in writing it shall abbreviate it to mc. Now, bearing in 
mind that the molecular weights of substances are the 
actual weights of their molecules in terms of some stand- 
ard, we may say that the molecular weights of all gases 
may be obtained in mc. by doubling their specific gravities 
referred to hydrogen as the standard; e.g., the specific 
gravity of HC1 is 18, the weight of its molecule in mc. is 
therefore 36; the specific gravity of NH, is 8.5, and the 
weight of its molecule is 17 mc. 

In most cases by chemical analysis we can determine 
accurately the proportions of the constituents which obtain 
in any compound ; thus, in the case of water, analysis 
shows that it is composed of one part by weight of hydro- 
gen to eight of oxygen, but this proportion of 1 to 8 holds 
also with the numbers 2 and 16, 3 and 24, 4 and 32, etc., 
and from the proportion alone we cannot tell which of 
the numbers (9, 18, 27, 36, etc.) is the molecular weight 
of water vapor, but by finding the specific gravity of water 
vapor (which is 9) and doubling it, we are enabled to 
decide that 18 is the molecular weight, that is, a molecule 
of water vapor weighs 18 mc. 

It should be observed that the determination of the 
specific gravity of a compound gas is a less accurate opera- 
tion than the analysis of the gas. The analysis gives an 
accurate number (the combining number of the gas or gases 
under consideration), and the specific gravity merely tells 
what multiple of that number to take. 

Thus from the law of Avogadro we are enabled very 
simply to decide whether a number is the molecular weight 
or a multiple or sub-multiple of it. This method of deter- 
mining molecular weights is clearly only applicable to 



ESSENTIAL PRINCIPLES. 35 

volatile substances, the molecular weights of the non- vola- 
tile substances must be determined in other ways. 

In this method hydrogen must be one of the constituent 
elements, or the atomic weight of one of the constituent 
elements must be known in terms of hydrogen as standard. 

OTHER METHODS OF DETERMINING MOLECULAR WEIGHTS. 

The determination of the molecular weights of substances from their 
gaseous specific gravities is the most important but not the only method 
for determining molecular weights. Several other methods have become 
available and will be briefly outlined. 

Molecular Weights from Osmotic Pressure. The mixing of dis- 
similar substances, gases, liquids, or solids in solution, through mem- 
branous diaphragms is in general termed osmose. Membranous bodies, 
such as rubber, parchment, etc., permit the passage of molecules of dif- 
ferent substances with very unequal facility. If a solution of a substance 
be separated from a quantity of the pure solvent by a proper diaphragm 
or osmotic membrane, a certain pressure will be exerted on the membrane 
from the side of the dissolved substance. This pressure is called osmotic 
pressure. 

It has been found that the osmotic pressure is conditioned by the 
following laws : 

(1) The pressure is directly proportional to the concentration of the 
solution, or to the weight of the dissolved substance in a unit of volume 
of solvent. 

(2) The pressure varies directly with the absolute temperature, for 
constant volume. • 

(3) The same osmotic pressure can be obtained by dissolving quantities 
of substances proportional to their molecular weights in equal volumes of 
the same solvent at the same temperature. 

These laws form the basis of the theory of solutions which has been 
thus stated by van't Hoff : the osmotic pressure of a substance in solution 
is the same as the gas pressure which would be observed if the dissolved 
substance alone, in gaseous state, occupied the volume of the solution at the 
same temperature. 

Many classes of substances, notably the aqueous solutions of inorganic 
acids, bases, and salts, do not conform to the above relations.; but many 
organic solutions do, and when the osmotic pressure can be found it gives 
a means for determining molecular weights. 



36 INTRODUCTORY OUTLINES. 

Molecular Weights by Depression of Freezing-point. It has been 

shown that when weights of substances proportional to molecular weights 
are dissolved in equal weights of the same solvent, they lower the freez- 
ing-point of the solvent to the same extent. From this generalization it 
is evident that the molecular weights may be determined. This method is 
called the cryoscopic method of determining molecular weights. 

Molecular Weights by Lowering Vapor Pressure. A precisely sim- 
ilar law holds with regard to the effects of a dissolved substance upon the 
vapor pressure of the solvent. AVhen weights of substances proportional 
to molecular weights are dissolved in equal weights of the solvent they 
lower to the same extent the vapor pressure of the solvent. This fact 
may also be used to determine molecular weights. In the method involv- 
ing the lowering of vapor pressure, it has been found more easily practi- 
cable to determine the elevation of the boiling-point. The last two 
methods are subject to the same restrictions as that by osmotic pressure, 
i.e., they are not in general applicable to inorganic solutions. The sup- 
posed explanation of this fact will be referred to subsequently. 

Determination of Atomic Weights from Considerations of 
Avogadro's Law. From what lias been said it is evident that 
the determinations of atomic weights by the methods thus 
far given were unsatisfactory, because of our inability to 
decide as to the number of atoms entering the molecule. 
It will now be shown how we may obtain other informa- 
tion on this point. 

Let us compare the gaseous compounds of the elements 
we are studying with each other. It is evident that a 
compound molecule must contain at least one atom of 
each constituent element, therefore, if we find the smallest 
weight of an element in any compound we shall have 
iound its atomic weight. 

Take, for example, the compounds of hydrogen in Table 
I. In the first column are given the specific gravities ; the 
doubles of these numbers in the second column give the 
molecular weights in microcriths ; in the third column is 
given the per cent of hydrogen in the molecule, or the 
proportion which the weight of hydrogen in the molecule 



ESSENTIAL PRINCIPLES. 



3? 



bears to the whole weight of the molecule ; in the fifth 
column this weight of hydrogen is given in mc.'s. 



TABLE I. 



Hydrochloric acid. . . . 

Hydrobromic acid 

Water vapor 

Sulphydric acid 

Ammonia 

Phosphorus trihydride. 

Marsh gas 

Olefiant gas 



Specific 
Gravities 



18.1 
40.0 

9.0 
17.0 

8.5 
17.0 

8.0 
14.0 



Molecular 
Weight 
in mc. 



36.2 
80.0 
18.0 
34.0 
17.0 
34.0 
16.0 
28.0 



Proportion 


Weight 


of 


of Hin 


Hydrogen. 


mc. 


.0277=^ 


1 


• 0125= A 


1 


.iin=A 


2 


.0588=3 8 ¥ 


2 


.1765= T 3 T 


3 


.0882= ¥ \ 


3 


.250 =A 


4 


•161 =A 


4 



Symbols. 



HC1 
HBr 
OH 3 
SH 2 
NH, 
PH 3 
CH 4 

CqBU 



It is thus seen that the smallest weight of hydrogen in 
any of these compounds is one mc, and this is the small- 
est weight yet found in any compound. It also appears 
from the table that the amounts found in the other com- 
pounds are multiples of this small weight. 



TABLE II. 



Water vapor . 

Carbon monoxide 
Carbon dioxide . . 
Sulphur dioxide . . 
Sulphur trioxide . 
Oxygen 



Specific 
Gravities. 



9 

14 
22 
32 
40 
16 



Molecular 
Weight 
in mc. 



18.0 

28 

44 

64 

80 

32 



Proportion 


Weight 


of 


of Oin 


Oxygen. 


mc. 


.8889=4f 


16 


.5714=^1 


16 


.7272=|f 


32 


.50 =f| 


32 


.60 =n 


48 


1.00 =|f 


32 



Symbols. 



OH 3 
CO 
C0 2 
S0 2 

S0 3 

o a 



A similar comparison of the compounds of oxygen and 
chlorine in Tables II and III, shows that the smallest 
amounts of these elements which enter are respectively 16 
and 35.5 microcriths, and no smaller weights have ever 
been found to enter ; again, all larger amounts are multiples 
of these smaller weights. 



38 



INTRODUCTORY OUTLINES. 
TABLE III. 



Hydrochloric acid 

Acetyl chloride 

Carbonyl chloride 

Phosphorus trichloride . . 
Carbon tetrachloride . . . 
Chlorine - 



Specific 
Gravities. 



18.1 
39.1 
49.2 
63.2 
76.4 
35.2 



Molecular 
Weight 



36.2 
78.2 
98.4 
136.4 
152.8 
70.4 



Proportion 
of CI. 



.9724 = ; 

.452 = 

.715 = 

.774 = 

.922 = 



35.2 

2 

35.2 

78.2 
70.4 
93.4 
105.6 
136.4 
140.8 
152.8 
0.4 



1.000 -gj 



Weight 
of CI 
in mc. 



35.2 
35.2 

70.4 
105.6 
140.8 

70.4 



Symbols. 



HC1 

C 2 H 3 0C1 

COCl 2 

PC1 3 

CC1 4 
CL 



These facts lead irresistibly to tlie conclusion that these 
smallest weights are our chemical units or atoms, and the 
larger amounts are exact multiples because they contain 
two or more atoms. The law T of Avogadro then gives us 
the means of deciding as to the molecular weights of gaseous 
substances, and by a comparison of the various compounds 
we select the smallest weight of an element which enters 
any compound as the atomic weight. The number of times 
this weight is contained in the other molecules gives the 
number of atoms of the element which enter them. 

It can now be seen that had we not taken the weight of 
the half-hydrogen molecule as the standard for molecular 
weights it would have been necessary to express the smallest 
amounts of hydrogen which enter certain compounds by 
one-half. Our standard mc. is the smallest mass of matter 
w T hich has yet been separated from any compound. It is 
the chemical atom, and since it is the half molecule, the 
molecule of hydrogen evidently contains two atoms. 

It should be remembered that the atomic weights depend 
upon the assumption that the same proportions which exist 
between the constituents of any compound, exist between 
the constituents of the molecules of said compound. Such 
is the only rational assumption, and these atomic weights 
are the relative weights of the atoms or chemical units of 



ESSENTIAL PEINCIPLES. 39 

different substances, or the actual weights of the different 
atoms in terms of the weight of the hydrogen atom taken 
as unity. 

Compounds sometimes contain the elements in other 
proportions than that of atomic weights, but the variation 
from atomic proportions arises from the fact that molecules, 
as already stated, are formed by the union of an atom of 
one kind with one, two, or three of another kind, or two of 
a kind with three of another, etc., etc. These different 
proportions are all combining or equivalent weights, and it 
is clear that they must be multiples or sub-multiples of the 
atomic weights. When elements unite in the proportion 
of one atom to one of another kind, the equivalent weights 
are the same as atomic weights, but they are different when 
the atoms unite in other proportions. 

The relations between specific gravities and adopted 
molecular weights are not usually so exact as is indicated 
in Tables I, II, and III. The numbers there given (specific 
gravities) may be considered as corrected by the results of 
chemical analysis. 

From certain of their volatile compounds, by the appli- 
cation of Avogadro's law, the atomic weights of the follow- 
ing thirty-eight elements have been determined : 

Aluminum," antimony, arsenic, boron, bromine, bismuth, 
carbon, cadmium, chlorine, chromium, copper, fluorine, 
gallium, hydrogen, indium, iodine, iron, lead, mercury, 
molybdenum, nickel, nitrogen, osmium, oxygen, phos- 
phorus, selenium, silicon, sulphur, tantalum, tellurium, 
thorium, titanium, tungsten, vanadium, zinc, and zirconium. 

By this method alone four of the elements named (alum- 
inum, copper, gallium and iron) have atomic weights double 
those usually assigned them. 

Number of Atoms in Elementary Molecules. When the 
atomic and molecular weights of an element are known it 
is evident that the quotient of the latter by the former 



40 



INTRODUCTORY OUTLINES. 



gives the number of atoms in the molecule. The molecular 
weights of thirteen of the elements have been determined 
from their specific gravities in the gaseous state and thence 
the number of atoms in their molecules. The elements re- 
ferred to are given in the subjoined table, together with the 
relations between their atomic and molecular weights : 



Elements. 


Molecular Weight. 

Atomic Weight. 

Number of Atoms 

in Molecule. 


Cadmium 


1 
1 
1 
2 
2 
2 
2 
2 
2 
2 
2 
2 
4 
4 


Mercury 

Zinc 

Hy d rogen 


Chlorine 


Nitrogen 

Tellurium 

Oxygen 


*Bromine 

*Iodine ... 


*Selenium 

*Sulphur ... 

Phosphorus 

Arsenic 





It is thus seen that cadmium, mercury, and zinc are monatomic and 
phosphorus and arsenic are tetratomic, the others were diatomic under the 
conditions of the experiments. Those elements marked with an asterisk 
varied in specific gravity with certain variations of temperature. Thus, 
sulphur at a lower temperature had six atoms in a molecule, and iodine, at 
a higher temperature than that employed in the table, had one atom in the 
molecule. 

Most of the elementary bodies thus appear to be 
diatomic. That this conclusion is involved in the law of 
Avogadro may also be seen from the following considera- 
tion. It is known that one volume of hydrogen combines 
with one volume of chlorine to form two volumes of HC1 ; 
from the law, each of the two volumes of HC1 contains as 
many molecules of HC1 as each of the original volumes 
contained molecules of H and CI respectively ; now suppose 
that the volumes of H and CI each contain n molecules of 



ESSENTIAL PRINCIPLES. 41 

H and CI respectively, the two volumes of HC1 must each 
contain n molecules, and as each molecule of HC1 must con- 
tain at least one atom of H and one of CI, there must have 
been at least 2n atoms of each of these elements, and con- 
sequently two atoms to each of the n molecules. In the 
same manner, by considering the fact that one volume of 
oxygen combines with two volumes of hydrogen to form 
two volumes of water vapor, we arrive at the conclusion 
that the molecule of oxygen contains two atoms, and by 
similar considerations of certain of their compounds the 
molecules of nitrogen and sulphur may be shown to con- 
tain two atoms. 

These are unavoidable conclusions from the law of Avogadro, but there 
is also some independent evidence that certain molecules of elements 
contain two atoms. Thus it was found that carbon burned in the protoxide 
of nitrogen produces more heat than when burned in, oxygen. A natural 
explanation of this fact is found in the supposition that it requires more 
heat to decompose the molecule of oxygen (it being composed of two atoms) 
than it does to decompose the molecule of the protoxide of nitrogen. 
Again, the nascent state which has been referred to as favorable to 
chemical action may be conceived to be due to the uncombined condition 
of the elementary atoms when just liberated from some previous com- 
bination. Thus, when hydrogen gas is passed through nitric acid it pro- 
duces no chemical change, but if produced in the acid it decomposes some 
of it. The molecules above referred to each have two atoms, but such is 
not the case with all elementary molecules. 

Again, the relations between the specific heats of gases at a constant 
volume and a constant pressure are not exactly what they should be from 
a consideration of the external work done ; it requires more heat to raise 
the temperature of a gas under constant volume than* it should, in propor- 
tion to that required under constant pressure. Now it may be supposed 
that a portion of the heat is consumed in the first case in producing a motion 
among the particles of the molecules which does not appear as change of 
temperature, and if the supposition be correct, then the discrepancy re- 
ferred to should not be observed in a gas whose molecule contains one atom. 
The relation between the specific heat of mercury vapor at a constant 
pressure and constant volume was found to accord exactly with theory, 
which seems to be a physical proof that the mercury molecule has but one 
atom. 



42 INTRODUCTORY OUTLINES. 

Isomorphous Relations. Bodies which, crystallize in the 
same or in very similar forms are said to be isomorphous, 
and the fact that many compounds of similar chemical 
constitution do crystallize in the same form led some 
chemists to believe that the same crystalline form assured 
the same atomic constitution of the respective molecules 
of the substances, — that an equal number of atoms arranged 
in the same way or united in the same way, gave the same 
crystalline form. 

It is now known that when the term isomorphism is 
used in the above sense the conclusion is not warranted. 
If, in addition to the same crystalline form, we impose the 
condition that the bodies shall be capable of producing from 
solutions homogeneous crystal forms containing varying 
proportions of the two ingredients, the idea of isomorphism 
becomes much more restricted, and the conclusions which 
result from its application in fixing atomic weights are gen- 
erally satisfactory. Thus, it is known that aluminum and 
oxygen unite in only one proportion, 17.9 of aluminum to 
16 of oxygen, but this same proportion exists in the 
numbers of 

Aluminum and Oxygen. 

35.8 32 

53.8 48 

71.6 64 

and the atomic weight assigned to Al will depend upon 
the constitution assigned to the oxide. If the oxide be a 

• Oxygen. Aluminum. 

monoxide, we shall have AlO = 16 17.9 

dioxide, we shall have A10 2 = 32 35. S. 

trioxide, we shall have A10 s = 48 53.7 

sesquioxide, we shall have ALO, = 48 ■< 

(26.9 

The numbers in the last column are the weights which 

must be assigned to the atom of aluminum according to 



ESSENTIAL PRINCIPLES. 43 

the several modes of constitution indicated in the first 
column. The constitution of the oxide alone does not 
enable us to decide between the different formulae, but as 
the aluminum oxide is isomorphous with the sesquioxide 
of iron, it is assumed to be a sesquioxide; its atomic weight 
thus becomes fixed as 26.9. This determination requires 
the atomic weight of oxygen to be known. 

The utility of this law is limited in application to 
groups of closely allied substances, and its indications 
become more valuable when connected with conclusions 
from other physical laws. The law of isomorphism was 
first enunciated by Mitscherlich in 1819. 

Volume Relations of Elements and Compounds. Under the 
law of Avogadro we have seen that when hydrogen is used 
as the standard for specific gravities and the half-hydro- 
gen molecule as the standard for molecular weights, the 
specific gravities of gases are the halves of their molecular 
weights. As most elementary gases are diatomic, it follows 
that the atomic weights and specific gravities of elementary 
gases are given by the same numbers ; one-half their molec- 
ular weights. Since specific gravities are given by the 
weights of equal volumes, it follows that equal volumes of 
elementary gases contain atomic proportions by weight. 
From the above relations it is readily seen that the number 
of volumes of the diatomic elementary gases which comhine 
to form a compound gas are indicated by the number of 
atoms of each element which enter the molecule of the 
compound gas. Thus, to form 

HCl there are required 1 vol. H and one vol. 01 

NH 3 there are required 1 vol. 1ST and three vols. II 

OH 2 (water vapor) there are required 1 vol. O and two vols. H 

Research widely extended has proven that, with a few 
exceptions, which may yet disappear, the molecules of 
compound gaseous bodies occupy twice the space of the 



44 INTRODUCTORY OUTLINES. 

hydrogen atom, no matter how many atoms of the elemen- 
tary gases enter the compound molecule. Thus, each of 
the molecules HC1, NH 3 , CH 4 , C 2 H 4 , CO, etc., occupies 
twice the space of the hydrogen atom. 

Since the same proportions exist between the quantities 
of the elements which form the whole body as do between 
the quantities which form the molecule, it follows that no 
matter how many volumes of elementary gases combine 
to form a compound gas of the first order, they are all con- 
densed to two volumes in the compound. All molecules, 
whether of the first or a higher order, occupy equal spaces, 
hence the same law of condensation holds in combinations 
of higher order than the first. 

This law of condensation is illustrated in the examples 
below. 

2 vol. H +1 vol. O give 2 vol. water vapor = OH 2 

2 vol. CI +1 vol. O give 2 vol. hypochlorous anhydride = C1 2 

2 vol. N +1 vol. O give 2 vol. nitrogen protoxide = N 2 

1 vol. CI +1 vol. H give 2 vol. hydrochloric-acid gas = HC1 

1 vol. N +3 vol. H give 2 vol. ammonia = NH 3 

2 vol. CO +2 vol. CI give 2 vol. carbonyl chloride = COCl a 
2 vol. C 2 H 4 + 1 vol. O give 2 vol. ethene oxide = C 2 H«0 

Apparent Exceptions to the Law of Volumes. From 
the foregoing considerations it is seen that the molecules of 
gaseous bodies are believed to occupy equal spaces, twice 
the space occupied by the hydrogen atom, and that their 
vapor densities referred to hydrogen are the halves of their 
molecular weights. There are a few apparent exceptions to 
this law, but the exceptions are believed to be due to molec- 
ular changes which take place in the bodies under the in- 
fluence of heat during the determination of their vapor 
densities, and that there is no occasion as yet to doubt the 
validity of Avogadro' s law. Among the bodies which were 
first thought to be exceptions may be mentioned 

PC1 5 , JS T H 4 C1, and C 2 H 4 2 . 



ESSENTIAL PRINCIPLES. 



45 



The quotient obtained by dividing the atomic weight of a 
simple body by its density is called the atomic volume, and 
that obtained by dividing the molecular weight of a body 
by its density is called the molecular volume. If matter 
were continuous these quotients would give the relative 
volumes of atoms and molecules. 

Specific Heats and Atomic Weights. The investigations of 
Pettit and Dulong in relation to the specific heats of the 
solid elements developed the fact that their specific heats 
are very nearly inversely proportional to their atomic 
weights, so that if atomic proportions, by weight, of these 
different elements be taken, the quantity of heat to change 
the temperature of these proportions through equal inter- 
vals is the same in all. 

In the following table a number of the solid elements are 
arranged according to their determined specific heats, be- 
ginning with those having the greatest : 





H. 


A. 


HXA. 
6.6 


Lithium 


0.941 


7 


Sodium 


0.293 


22.9 


6.7 


Aluminum. . . 


0.214 


26.9 


5.8 


Potassium. . . 


0.166 


38.9 


6.5 


Iron 


0.114 
0.109 


55.5 

59 


6.1 
6.4 


Nickel 


Copper 


0.0952 


63.1 


6 


Zinc 


0.0955 
0.0570 


64.9 

107.1 


6.2 
6.1 


Silver. ....... 


Tin 


0.0562 


118.1 


6.5 


Gold 


0.0324 


195.7 


6.3 


Platinum. . . . 


0.0324 


193.3 


6.1 


Lead 


0.0307 


205.4 


6.3 



In the first column are the specific heats, in the second 
the atomic weights, and in the third the product of these 
numbers ; water is taken as the standard for specific heats. 
This table exhibits the inverse relation existing between 
atomic weights and specific heats and the products all fall 



46 INTRODUCTORY OUTLINES. 

between the numbers 5.4 and 6.9 ; the mean value when all 
the solid elements are considered is usually given as 6.4. It 
is true that there are variations from this number, but the 
variations are slight and are probably due to the causes 
which influence the thermal condition of bodies and render 
the exact determination of specific heats uncertain. 

Since the announcement of Pettit and Dulong in 1819, 
that the atoms of all elements have the same capacity for 
heat, or the same specific heat, many facts have been 
accumulated in favor of the generalization and render it 
very probable that it is correct. 

This number (6.4) is frequently called the atomic heat 
of elements. 

This law gives us a ready means for the determination 
of the atomic weights of elements when their specific heats 
are known, it being only necessary to divide the number 
6.4 by the specific heat. However, the difficulty of deter- 
mining specific heats accurately limits very much this 
method of arriving at atomic weights, but the law enables 
us to decide with certainty between two or more possible 
hypotheses. 

We have seen that analysis will give the proportions of 
the constituents of a compound with a great degree of 
accuracy, and if we can decide as to the number of atoms 
of the respective elements in the compound the atomic 
weights become known, e.g., analysis shows that silver 
chloride contains 107.1 parts of silver and 35.2 parts of 
chlorine. With only this fact we cannot tell whether there 
be one or more atoms of silver, but by dividing 6.4 by the 
specific heat of silver (.057) we get 112, a number so nearly 
coinciding with the result of analysis as to show beyond 
doubt that there is but one atom. As the result of analysis 
is more reliable than the determination of specific heat, we 
accept 108 as the weight of the atom of silver, the specific 
heat merely deciding us as to the number of atoms in the 



ESSENTIAL PRINCIPLES. 



47 



molecule of the compound. This method requires that the 
atomic weight of one of the combining elements be known. 

The specific heats of the elementary bodies have not 
been determined at any common temperature, so that the 
values found are not strictly comparable. The specific 
heats of the elements generally vary with the temperature, 
but there are certain temperature intervals, different for 
the different elements, between the limits of which the 
specific heats are nearly constant. For this interval only 
is the law of Dulong and Pettit true. 

The following forty-nine solid elements have had their 
specific heats determined directly : 



Aluminum 


Cobalt 


Magnesium 


Selenium 


Antimony 


Copper 


Manganese 


Silicon 


Arsenic 


Didymium 


Mercury 


Silver 


Boron 


Gallium 


Molybdenum 


Sulphur 


Beryllium 


Gold 


Nickel 


Sodium 


Bismuth 


Indium 


Osmium 


Tellurium 


Bromine 


Iodine 


Palladium 


Thallium 


Carbon 


Iridium 


Phosphorus 


Thorium 


Cadmium 


Iron 


Platinum 


Tin 


Calcium 


Lanthanum 


Potassium 


Tungsten 


Cerium 


Lead 


Rubidium 


Uranium 


Chromium 


Lithium 


Ruthenium 


Zinc 




Zirconium 





With but few exceptions the product of the specific 
heat into the atomic weight is approximately equal to 6.4, 
all falling between 6 and 7. The exceptions are boron, 
beryllium, carbon, gallium, and silicon. 

The law of equal atomic heats has been found in many instances to 
extend to chemical compounds in the case of bodies of similar atomic 
composition. In such cases the products of the specific heats into molecu- 
lar weights are nearly constant and are equal to as many times 6.4 as 
there are atoms in the molecule. The application of the law has been 



48 INTRODUCTORY OUTLINES. 

extended so as to justify the statement that the specific heat of the com- 
pound is the sum of the specific heats of its elementary components. This 
principle has been applied to many compounds for the determination of 
atomic weights. 

In the case of the solid elements, when their specific heats are deter- 
mined under specified conditions, it may be considered that there are no ex- 
ceptions to the law of Pettit and Dulong, so closely do the products of the 
atomic weights and specific heats approximate to a common number. The 
difficulty of determining how much of the heat transferred to gases and 
compounds is consumed in performing internal and external work, and 
how much in simply affecting temperature, renders it as yet difficult to 
bring them under the general law. It is a reasonable expectation that this 
will be done as our knowledge of molecular structure increases. 

VALENCY OR QTJANTIVALENCE. 

We have already seen that the atomic and equivalent 
weights of some of the elements are the same, and in 
others that the atomic weight is some multiple of the 
equivalent weight. In other words, that atoms of certain 
elements can only replace or combine with atoms of other 
elements in the proportion of one to one ; in other cases, 
this equivalency or substitution can occur in the propor- 
tion of one atom to two or more of another kind ; thus, 
chlorine, bromine, and iodine always combine with hydro- 
gen in the proportion of one atom to one, oxygen and 
sulphur one atom to two of hydrogen, and when sodium 
acts on hydrochloric acid each atom of sodium replaces 
one of hydrogen, as Na -f- HC1 = JNaCl -f H ; with zinc 
under the same circumstances each atom replaces two of H, 
as Zn + 2HC1 = ZnCl 2 + H 2 . This difference of combining 
or replacing power is generally called valency. The valency 
of an element may be defined as the number of equivalent 
weights contained in its atomic weight. 

If we select the hydrogen atom as the standard for refer- 
ence, the valency of any other element is known by the 



ESSENTIAL PRINCIPLES. 49 

number of hydrogen atoms that its atom is equivalent to 
in the sense just given. The elements have been classed 
according to degree of valency as univalent, bivalent, 
trivalent, etc., and are called monads, dyads, triads, tetrads, 
pentads, etc. The elements of even valency are also called 
art lads and those of uneven valency perissads. The 
valency is sometimes indicated by putting dashes or Roman 
numerals after the symbols of the elements, thus, O 11 , C IV , 
P v , etc. 

Another method of indicating the valencies of elements 
and the manner in which they are supposed to be satisfied 
in combination is by graphic formulae ; thus, water may be 
represented by 

H— O— H 
and carbon dioxide by 

0=C=0, 

marsh gas by 

H 

I 
H— C— H. 

I 
H 

These are called graphic or structural f ormulse, and indicate 
nothing more than the degree of valency of the elements 
and the manner in which they may be supposed to be 
satisfied in combination. The short lines extending 
between the atomic symbols are intended to express the 
valence action or combining capacity exerted between the 
atoms connected. 

The valency of an atom as shown by its replacing power 
corresponds exactly with that shown by its combining 
power, that is, an atom capable of replacing a certain 
number of monad atoms is also capable of combining with 
the same number ; thus, the atom of zinc which is capable 
of replacing two atoms of hydrogen is also capable of 



50 INTRODUCTORY OrTLTXES. 

combining with two atoms of CI. or Br. monad elements. 
This property of valence is inherent to radicals, already 
defined, as well as to elements, and is manifested when 
they change places in reactions with other radicals or 
elementary atoms ; some radicals are capable of combining 
with or replacing one monad atom and others more than 
one. 

In the above graphic formulae it is seen that the units 
of valency of each atom are represented as satisfied by 
combination with units of valency of other atoms. Such 
compounds are sometimes called normal or saturated com- 
pounds, and in the molecule of such a saturated compound 
the sum of the perissad atoms is always an even number. 
This is the law of even numbers^ and it is of necessity true 
in such saturated compounds, from the above definition. 
To form a saturated molecule under the hypothesis of 
valency it is not. however, necessary that the units of 
valency of each atom shall combine with the units belong- 
ing to atoms of different elements. They sometimes combine 
with those of other atoms of the same element, thus, 

c— c c— c— c 

Hj H: H 3 Ho rT 3 

which are saturated hydrocarbons.* 

By considering the above formula? it is evident that if 
an atom of any kind could be removed the balance of 
valency would be destroyed and a certain number of units 
of valency would be left unsatisfied : thus, if from the 
saturated molecule CJL we remove one atom of H. we get 
the compound CH S : from SO s remove one atom of and we 
get SO... These unsaturated molecules constitute the com- 

*I: is evident from this consideration that there is a lack of precision in the 
definition of a "saturated molecule." Other definitions have been proposed, 
but are upon the whole not more satisfactory. 



ESSENTIAL PRINCIPLES. 51 

pound radicals already referred to, and the valency of a 
compound radical may generally be said to equal the 
valency of the atom or atoms which the saturated molecule 
may be considered to have lost. As already stated, it is 
only a few of these non-saturated molecules that exist in a 
free state, as CO, S0 2 , etc.; in other cases, two of the un- 
saturated molecules combine with each other, and then 
again they appear as transferable compounds in chemical 
reactions without isolation. The tendency of unsaturated 
compound molecules to combine with each other seems to be 
analogous to the action of the atoms of elementary bodies ; 
we have already seen that these elementary atoms seldom 
exist in the free state, but are combined in pairs. It may 
also be stated that generally the compound radicals which 
exist separately have an even valency. 

Variable Valency. The valency of an element as above 
expressed, and as determined by the number of atoms which 
enter its compounds, is not a constant and unvarying prop- 
erty of many elements. This is especially shown by their 
varying degrees of combining power; thus, tin forms two 
compounds with CI, viz. : SnCl 2 and SnCl 4 , and phosphorus 
forms PC1 3 and PC1 5 . Numerous other examples might be 
given. Thus arises the difficulty of classifying the elements 
according to valency. The influence of the property which 
we have termed valency, in its variation, brings about the 
same results which come from the law of multiples ; the 
difficulty in determining valency is the same as in fixing 
equivalent weights, and follows from the combination of 
elements in different proportions. The atomic weight is 
equal to the equivalent weight multiplied by the valency, 
and when either of the latter is determined the other will 
be also. 

When the same element shows different degrees of 
valency some one degree is generally more common and 
the compounds resulting from its action more perma- 



52 INTRODUCTORY OUTLINES. 

nent than any other, and in several elements, as hydrogen 
and the alkaline metals, the valency has been found in- 
variable. 

Of the multivalent elements the variation in valency 
usually takes place by a loss or gain of two units of valency, 
so that the possible conditions of the same element are 
usually all even or all odd ; thus, CI may be univalent, 
trivalent, quinquivalent, and septivalent; S may be bivalent, 
quadrivalent, or sexvalent. 

Valency and Affinity. Valency and affinity are properties 
of the atoms which, as yet understood, are distinct and dif- 
ferent. Affinity is conceived as the property of matter by 
virtue of which compounds are formed and exist. Valency 
has reference to saturating power or to the number of 
atoms that enter the molecule of the compound. The 
greatest affinity may be exerted between elements of small 
valency, and elements with variable valency often exercise 
their smaller valency when combining with those for which 
they have greatest affinity, and their higher valency in 
combining with those for which they have least affinity. 
Affinity is related to the energy of action, while the idea 
of valency refers more to the structure of the molecule. 

Thus valency, like affinity, seems to be a relative property 
of the elements, depending upon a number of conditions, 
among which may be mentioned temperature, the influence 
of atoms upon each other, and possibly the relative quanti- 
ties of the acting substances. 

The abstract idea of valency has reference only to the numerical 
capacity of saturation, atom-fixing power of the different atoms, but any 
concrete conception of valency invariably suggests the arrangement of 
atoms in the molecule, attempts to formulate the structure of the mole- 
cules of bodies and to express the relation between the atoms thereof. The 
hypothesis of valency involves many considerations and permits the expres- 
sion of a large number of facts and conclusions in a concise and intelligible 
manner ; but the property of valency has not been shown to be an in' 
variable factor in the phenomena which result in chemical compounds. 



ESSENTIAL PRINCIPLES, 53 

We have here introduced only such considerations of 
the valency of elements as are most essential in enabling 
the student to readily express correctly in chemical lan- 
guage the ordinary reactions, the results of the general 
laws of combination. Those considerations are, in the 
main, independent of all arbitrary assumptions as to the 
nature of the property called valency, and depend upon 
experimental observation. 

PROPERTIES OF CERTAIN IMPORTANT SUBSTANCES. 

In connection with the principles already set forth it 
will be of great advantage to the student to commit to 
memory the specific properties of certain bodies. A 
knowledge of these properties will facilitate the anticipa- 
tion and expression of many reaction processes. The class 
arrangement will save many special efforts of memory. 
The statements apply to very nearly all the bodies belong- 
ing to the classes of salts indicated, and may by the 
general student be considered as applicable to all the im- 
portant salts he will be called upon to consider. 

I. Ordinary valency of elements named : 

H' Na' S" Hg" Fe" 

Cr Ag' Cn" Zn" O 

K' . 0" Pb" Ba" N v 

II. The nitrates are all soluble in water. 

III. All dichlorides are soluble in water except the 
dichloride of lead. All monochlorides are soluble in water 
except those of silver and mercury. 

IY. All sulphates are insoluble in alcohol ; all are 
soluble in water, except that of barium, which is insoluble 
in water, and those of calcium, strontium, lead, and silver, 
which are slightly soluble in water. 

The carbonates are all insoluble in water, except those 
of the alkalies ; and are all decomposed by heat, exivpt 



54 INTRODUCTORY OUTLINES. 

those of the alkalies. All carbonates are soluble in water 
containing carbon dioxide in solution. All carbonates are 
decomposed by sulphuric, nitric, or hydrochloric acid, the 
carbon dioxide escaping with effervescence. 

STOCHIOMETRY. 

That class of chemical computations which can be made 
from a consideration of the numerical relations of atomic 
weights and the volume relations of elements and com- 
pounds is called stochiometricaL From a knowledge of 
preceding principles many such computations are possible. 
It has already been stated that the symbols of the respec- 
tive elements represent atoms, and that the atoms of differ- 
ent elements have different weights, that the molecular 
weights of substances are the sums of the weights of the 
atoms in their respective molecules. In the most limited 
sense chemical symbols represent atomic weights of their 
respective elements in terms of the weight of the H atom, 
but in a more general sense, in all equations, reactions, and 
f ormula3 they stand for quantities proportional to atomic 
weights, and when the amount by weight of any one ele- 
ment in a formula or equation is given, the amounts of all 
the others become known. 

Percentage Composition. Thus, the formula for water is 
OH 2 , and from the relations expressed in the formula if 
either the amount of H or O is assumed, the amount of the 
other element is also known. 

From the formula for a substance it is evident that we 
may also readily compute its percentage composition; thus, 
the formula for alcohol is C 2 H 6 0, the molecular weight is 46, 
hence in 46 parts by weight of alcohol there are, 24 of C 

6 of H 
16 of 

46 






ESSENTIAL PRINCIPLES. 55 

hence in 100 parts we should have 

for C 46 : 24 : : 100 : x = 52.18 
for H 46: 6: : 100 : y = 13.04 
for O 46 : 16 : : 100 : z = 34.78 



100.00 



Having given the percentage composition of a substance 
we can also readily determine the numerical relations 
existing among the atoms, but not necessarily the actual 
number of atoms in the molecule ; thus, the percentage 
composition of acetic acid is 

C =40 
H = 6.67 
O = 53.33 



100.00 



Since these numbers are the relative weights of the elements 
in the substance, if we divide them by the atomic weights 
the quotients will express the relations existing among the 
numbers of atoms of the different elements. Performing 
the division referred to we have for the numerical relation 
of atoms 

^3.33H6.67^3.33) 

V 

which is evidently the same as 

Empirical and Molecular Formulae. The simplest expres- 
sion for the numerical relations existing among the atoms 
of a molecule of a substance is called its empirical formula ; 
that is to say, when we express the numerical relation 
among the atoms by the smallest numbers possible ; thus 
abov^, 'JvH 2 Oi is the empirical formula for acetic acid. 



56 INTRODUCTORY OUTLINES. 

The same relations exist among the numbers of atoms 
whether the formula be CiH 2 Oi, C 2 H 4 2 , or C 3 H 6 3 , etc. 

The formula which gives the exact number of atoms of 
each of the elements which enters the molecule of a sub- 
stance is called the molecular formula. It cannot be com- 
puted with certainty from the percentage composition 
alone, but if the molecular weight of the substance is 
known the problem admits of definite solution, for from 
the molecular weight we know the sum of the atomic 
weights, and can decide which of the formulae expressing 
the numerical relations among the atoms is the molecular 
formula. 

Thus, in the example above the molecular weight of 
the acetic acid is 60, hence it is evident that of the pos- 
sible formulae C 2 H 4 2 is the molecular formula of the acid. 
The molecular formula is always the same as, or a multiple 
of, the empirical formula. 

Problems Involving Weights. Since, as has been said, in 
the most general sense the symbols represent quantities 
proportional to atomic weights and formulae represent 
quantities proportional to molecular weights, it is easy to 
determine the amounts of the various substances indicated 
in any equation when the amount of any one is assumed. 
For this purpose it is only necessary to express the atomic 
and molecular weights of the different terms of the equa- 
tion and simple proportions will solve the problem. 

Thus, in the equation 

Zn + 2HC1 = ZnCl 2 + H 2 , 

expressing the action of Zn upon HC1, suppose we assume 
that Zn stands for 10 ounces of zinc, then to determine how 
much HC1 is indicated we proceed as follows : the atomic 
weight of Zn = 649 and the molecular weight of HC1 = 36.2 
The reaction indicates that for the transformation of 64.9 
parts of Zn there are required 2 X 36.2 = 72.4 parts of HC1 ; 



ESSENTIAL PRINCIPLES. 57 

hence the amount to transform 10 parts of Zn would be de- 
termined by the proportion 

64.9 : 72.4 : : 10 : x. 

The amounts of the other substances indicated as involved 
in the reaction under the supposition that 10 ounces of zinc 
are employed would be determined in exactly the same 
manner. 

It matters not whether some of the terms of the equation 
are simple atoms or whether all the terms are composed of 
molecules. The molecular and atomic weights of the dif- 
ferent terms express the relations existing between the 
amounts of the substances employed in the reaction, and 
from these relations the amounts of all the substances in- 
dicated can be determined when the amount of any one is 
assumed. 

Problems Involving Volumes. All of the above solutions 
depend upon the numerical relations of atomic weights, but 
a chemical equation expresses not only relative weights, but 
also relative volumes of the reagents and products when in 
a state of gas. We have seen that all gaseous molecules 
occupy equal spaces, and that gaseous atoms occupy one 
half the space of the molecule. Coupling these facts with 
the principles of notation explained, it is evident that the 
relative numbers of volumes in an equation of gaseous 
terms can be read off directly ; thus, 

2CO + 2 = 2C0 2 
and 

CH 4 + 4 = C0 2 + 2H 2 0. 

In the first equation, since molecules occupy equal spaces, 
it is seen that the number of volumes of C0 2 is the same as 
the number of volumes of CO, and the number of volumes 
of O involved is one half that of the other gases. In the 



58 INTRODUCTORY OUTLINES. 

second equation the relative volumes are : two of CH 4 , four 
of O, two of C0 2 , and four of OH 2 (vapor of water). 

It is often desirable to pass from volumes to weights, or 
the reverse, in the case of gaseous bodies. The problem is 
so simple as to require only the statement that in the first 
case we multiply the number of volumes by the weight of 
a unit of volume, and in the second case we divide the 
weight by the weight of a unit of volume ; volumes, of 
course, being always taken under standard conditions of 
temperature and pressure. 



CHAPTER II. 

CHEMISTRY OF THE NON-METALS AND THEIR 
COMPOUNDS. 

OXYGEN. 

Oxygen is the most abundant and widely distributed 
of the chemical elements. It exists in the uncombined 
state in atmospheric air, forming about one-fifth of its vol- 
ume ; it is there mixed with nitrogen, which constitutes 
nearly the entire bulk of the remaining four-fifths. 

In the free state oxygen is an essential to all forms of 
life. 

In the combined form it is an important constituent of 
most of the mineral and organic substances. In this form 
it constitutes eight-ninths, by weight, of water and about 
one-half, by weight, of silica and of the various silicates 
and limestones, which compose by far the greater portion 
of the earth' s crust. 

Oxygen was discovered by Priestley in England in 1774 
and called by him dephlogisticated air. In the following 
year it was independently discovered by Scheele in Sweden. 
It was named oxygen by Lavoisier. 

Physical Properties. Oxygen is a gas, tasteless, odorless, 
colorless, and perfectly transparent It is slightly soluble, 
water at 60° F. dissolving about .03 of its volume. By great 
pressure and low temperature it has been liquefied, and by 
further cooling solidified. Its specific gravity referred to 
hydrogen is given by its atomic weight ; it is thus seeD to 

59 



60 INORGANIC CHEMISTRY. 

be slightly heavier than atmospheric air; when liquefied 
it is lighter than water. 

Chemical Properties. Oxygen is remarkable for the wide 
range of its chemical action. With the exception of bro- 
mine and fluorine it forms compounds with all other ele- 
ments, and with the exception of seven elements it unites 
directly, without the intervention of a third substance. 

These combinations, as already stated, are called oxides, 
and the process is termed oxidation. 

The combination of oxygen with the other bodies is gen- 
erally accompanied by the develorjment of heat, but if the 
oxidation is very slow the heat may not be perceptible. 
If the oxidation be sufficiently rapid to produce light and 
heat it becomes a case of combustion. 

Combustion in a general sense is any chemical action 
accompanied by heat and light ; all ordinary cases of com- 
bustion in air are processes of oxidation, the light and heat 
being the result of the chemical union of the oxygen with 
the body burned. In most cases an elevation of temperature 
is necessary to bring about the union of oxygen with other 
substances ; with some bodies at ordinary temperature it 
unites slowly without sensible elevation of temperature, 
and with a few, rarjid oxidation takes place, producing 
combustion. 

Action on Non-Metals. Among the non-metals phos- 
phorus is the only element that combines with oxygen at 
the ordinary temperature. In the air it gives off white 
fumes and emits a pale phosphorescent light. It is then 
undergoing oxidation, and if it be finely divided true com- 
bustion will result. This may be readily accomplished by 
dissolving a little phosphorus in carbon disulphide and 
pouring the solution on blotting-paper ; when the solvent 
evaporates, the finely divided phosphorus exposes a large 
surface to the action of the air, and, the paper being a bad 
conductor, the temperature rapidly rises and brilliant com- 



NON-METALS. 61 

bustion results. In warm air a very slight elevation of 
temperature will cause phosphorus to burn, and this is 
sometimes brought about by the oxidation of the outside 
particles ; phosphorus must accordingly be handled with 
great care. 

Phosphorus produces a bright light when burning in the 
air, but the brilliancy is greatly increased when it is burned 
in pure oxygen, due to the more rapid combustion and 
consequent higher temperature. 

All substances which burn in air burn far more readily 
in pure oxygen. By the combustion of phosphorus in 
air phosphoric oxide is produced (P 2 5 ), which may be 
seen to rise in clouds from the burning phosphorus. This 
oxide is readily absorbed by water, forming meta-phos- 
phoric acid: (HP0 3 ). 

If a piece of wood charcoal be heated to redness at a 
single point and be plunged into a jar of oxygen, brilliant 
combustion takes place, the oxygen combining with the 
carbon, producing carbon dioxide (C0 2 ), which is a colorless 
gas. Pure carbon has to be heated very highly before it 
will combine with oxygen, and then the combustion is 
unattended with flame. 

Sulphur, when its temperature is raised to about 500° F., 
burns in air with a blue flame. In pure oxygen the bril- 
liancy is much increased ; in each case the product of com- 
bustion is sulphur dioxide (S0 2 , which readily unites with 
water, forming sulphurous acid. 

Action on Metals. Several of the alkaline and alkaline- 
earth metals (potassium, sodium, lithium, barium, calcium, 
and strontium) are readily oxidized in the air. 

Others of the common metals, as iron, lead, and mercury 
are scarcely acted upon by dry air, and gold, silver, and 
platinum not at all. Under the influence of high tempera- 
ture many of the metals burn readily. A magnesium ribbon 
will burn in air if the end of the ribbon be heated in a Bun- 



62 INORGANIC CHEMISTRY. 

sen burner; the light is almost insupportable to the eye. 
The burning of iron is also easily accomplished, and is best 
shown, in a small way, by wrapping one end of a softened 
steel watch-spring spirally around a little cylinder of char- 
coal and attaching the other end to a suitable holder, ignit- 
ing the charcoal and plunging the whole into a jar of 
oxygen. It burns very brilliantly, sending off a shower of 
sparks. The black oxide of iron, Fe 3 4 , is produced by the 
combustion. 

Zinc may be burned by a precisely similar arrangement, 
giving zinc oxide (ZnO). 

Iron can be prepared in such finely divided form that 
when exposed to air it will take fire spontaneously ; it is 
then called pyrophoric iron. 

The preceding illustrations, which might be extended 
indefinitely, are all cases of oxidation, and it is seen that 
oxidation may or may not produce the phenomenon of com- 
bustion. All ordinary combustion in air is but the oxida- 
tion of the body burned, oxygen being the sustaining 
principle of such combustion and also of animal life. All 
bodies which burn in air burn with increased splendor in 
pure oxygen. 

It is well here to recall the important fact already stated 
that the oxides of the non-metals are generally acid oxides, 
and those of the metals basic oxides. The former when acted 
upon by water give the substances which we have defined 
as acids, and the latter tend to neutralize these acids. So 
general is this tendency of the metallic oxides that any 
substance which forms a basic oxide may be defined as a 
metal, though it is not decided that every metal forms a 
basic oxide. 

Preparation of Oxygen. For laboratory and experimental 
purposes oxygen is most readily prepared from potassium 
chlorate (KC10 3 ) or manganese dioxide (Mn0 2 ). From 
either of these substances oxygen may be obtained by heat- 



NON-METALS. 



6a 



ing in suitable apparatus, the results being indicated by the 
following equations : 

KC10 3 (heated) = KC1 + 8 , 3Mn0 2 (heated) = Mn 3 4 + O a . 
To accomplish these results a higher degree of heat is 
required than is convenient, and it is customary and advis- 
able to mix with the chlorate from one-fourth to one-fifth its 
weight of the oxide, when the liberation of oxygen takes 
place at a lower temperature than when either substance is 
used alone. The mixture of potassium chlorate and man- 
ganese dioxide may be heated in a glass retort or Florence 
flask, the retort or flask being closed by a perforated cork 
into which fits a glass tube. The glass tube serves to con- 
vey the gas to a gas-holder or to a jar filled with water 
standing on a beehive shelf. The glass may be extended 
by rubber connection. This form of apparatus is of very 
frequent use in chemistry and is shown at Fig 1. The 




Fig. 1. 

manganese dioxide, or pyrolusite as it is called in min- 
eralogy, is not changed in this operation. The action of 
the manganese dioxide comes under the term of catalytic 
action and is not thoroughly understood, but the oxide 
probably passes to a higher state of oxidation and is then 
reduced. 

Oxygen may also be prepared by decomposing water 
(H 2 0) by electricity. In some laboratories both oxygen 
and hydrogen thus obtained are kept on hand in large 



64 IXORGAXIC CHEMISTRY. 

holders, the electricity being supplied by dynamo- 
machines. 

Oxygen may be prepared on a large scale directly from the atmosphere 
by passing a current c : air *ver a mixture of cans::: alkali and manganese 
dioxide ; alkaline manganates are thus formed. By passing steam over 
the heated manganates they are resolved into the original constituents 
with the liberation of oxygen. The operation can be made continuous. 

Fhere are many other methods by which oxygen may be prepared. 
Priestley, when he discovered oxygen, obtained it from the red oxide of 
mercury. 

OZONE. 

Ozone was discovered by Schcmbein in 1940. It appears to be a 
modified form :: oxygen in which it is found that there are three atoms 
in the molecule, instead of two as in ordinary oxygen. According to 
AYOgadro's law it should be one and a half times as heavy as common 
oxygen, and this has been determined to be the case by experiment. It 
exists in very small quantity in the atmosphere, und is found in the purer 
air of the country or the seaside more khan in thickly populated places. 
It has been estimated to constitute not more than one volume in a million 
volumes :: air. 

Physical Properties of Ozone. Under ordinary conditions ozone is a 
transparent gas showing a blue tinge vri r - v:e^ei along a glass tube a 
meter in length. The color deepens by pressure. The gas has a peculiar 
and listinct idor. It is more easily liquefied than pure oxygen ud the 
liquid has a blue color. TVhen heated :: 300" F. ozone is convene 1 ink 
:i _ . with an increase of half a volume. 

Chemical Properties. Ozone is chemically much more active than 
oxygen, sombining with many substances that wtygen will not affect. 1: 
will decompose potassium iodide, liberating the iodine. In the proses 
alkalies it will unite with nitrogen and convert it into nitric acid. It will 
oxidize silver and also a solution of indigo, bleaching the latter ; ordinary 
oxygen does not act upon these substances. Ozone acts upon many organic 
substances, and it is to this : act that its beneficial effect in the air is 
attributed. In most cases of oxidation the remaining oxygen appears to be 
:ne in volume as the original ozone. Air highly charged with ozone 
cannot be breathed with impunity, its action on the system resembling 
that of chlorine. 

Preparation of Ozone. Ozone is produced by the passage :: electric 
sparks through t :xjz^~ and is generally observed'::yi:s : :l:r wLer 



JTOiY-MBTALS. 65 

a spark electric machine is operated in the air. It is also produced during 
the decomposition of water by electricity, by the slow oxidation of phos- 
phorus and turpentine in the air. This latter fact has been suggested as 
an explanation of the acknowledged salubrity of pine regions. 

The presence of ozone may be detected by bringing into it a piece of 
paper moistened with a solution of starch and potassium iodide ; the ozone 
liberates the iodine, which gives a blue color with the starch. The test, 
however, does not insure the presence of ozone, as certain other substances 
will have the same action ; among these are chlorine, bromine, and nitrogen 
dioxide. 

HYDROGEN. 

Hydrogen rarely occurs in a free state under terrestrial 
conditions, though it has been found to a limited extent in 
certain volcanic emanations, in the gases given off by oil- 
wells, and occasionally occluded in meteorites. 

The spectroscope has shown it to be present in the 
atmosphere of several of the heavenly bodies, especially 
the sun. 

Hydrogen was discovered by Cavendish in 1766 and 
called by him inflammable air ; it was subsequently named 
hydrogen by Lavoisier. 

Physical Properties. Hydrogen is a transparent gas, taste- 
less, colorless, and odorless. It is the lightest substance 
known. Water is 11,160 times as heavy as hydrogen at 0° 
C. It is not poisonous, though animals cannot live in this 
gas alone, oxygen being necessary to life. Hydrogen being 
the lightest substance known, it is conveniently taken as 
the standard for the specific gravity of gases, that is to say, 
the standard to which other gases and vapors are referred. 

Owing to its great lightness hydrogen can be collected 
by downward displacement or poured upward from one 
vessel to another ; on account of this property it is em- 
ployed for filling balloons. 

Hydrogen is slightly soluble, water dissolving .02 of its 
volume at 0° C. and 30" barometric pressure. 

By great pressure and cold, hydrogen has been lique- 



66 



INORGANIC CHEMISTRY. 



fied, giving a steel-blue liquid. The conducting power of 
hydrogen for heat is, according to Magnus, greater than 
that of any other gas. Another remarkable physical prop- 
erty is its great power of passing through animal and 
vegetable membranes and porous substances generally. 
This property is called diffusive power, and it is a physical 
property common to all gases and vapors. The diffusive 
powers of gases are found to be inversely proportional 
to the square roots of their densities. Hydrogen accord- 
ingly diffuses far more rapidly than any other gas ; 
because of this property hydrogen is more difficult to con- 
fine than any other gas. It will leak through a stop- cock 
which will retain oxygen and ni- 
trogen, and it cannot be kept long 
in rubber bags, bladders, etc. 

The diffusive property of gases 
causes them to fill uniformly any 
space in which they may be 
placed. It also causes gases to 
mingle uniformly even against 
the force of gravity ; thus if two 
vessels, one containing oxygen, 
the other hydrogen, be connected 
by a narrow tube with the oxygen 
below, in a short time they will 
be uniformly mixed. The same 
result follows with any two gases 
that do not act chemically upon 
each other. 

The remarkable diffusive power of hy- 
drogen may be shown by the following 
experiment. Take an unglazed porous cup p IG# g # 

(a common battery cup answers well) and 

close the open end with a cork through which extends a glass tube ; then 
invert this cup and insert the tube into a tightly sealed bottle arranged 




NON METALS. 67 

with a jet tube as shown in Fig. 2. By placing a glass jar containing 
hydrogen over this cup the liquid may be forced out of the lower vessel 
in a jet several feet high. In this experiment the oxygen in the connected 
vessels passes out through the porous cup into the hydrogen jar, but 
the hydrogen passes in much more rapidly, and the pressure of the 
hydrogen added to that of the oxygen drives out the water. The true 
diffusion of gases depends upon <the motion of their molecules, but this 
diffusion is often complicated by the nature of the septa through which 
diffusion takes place. If the diaphragm exerts an adhesive or liquefying 
action on the gases, or if it is moistened with any liquid which exerts a 
solvent power on them, the simple diffusion passes into osmose or osmotic 
action. 

These processes are very important in nature : by true 
diffusion the uniform composition of the atmosphere is 
mainly maintained and the accumulation of noxious gases 
prevented ; by osmose the function of respiration is per- 
formed and the aeration of the blood accomplished. Cer- 
tain of the metals, as platinum and palladium, possess the 
power of absorbing and condensing within their pores 
large volumes of some of the gases. This action is called 
occlusion of gases. Certain meteorites have been found to 
contain a large amount of hydrogen, indicating that they 
have come from regions where hydrogen exists at greater 
pressure than in our atmosphere. 

The terms osmose and diffusion are also applied to the 
processes by which substances dissolved in liquids pass 
into solutions of less density through diaphragms, or 
against the force of gravity. 

Chemical Properties of Hydrogen. The chemical properties 
of hydrogen cause it to combine readily with several of the 
non-metals, but it shows little if any disposition to combine 
with metals. The most evident chemical characteristic of 
hydrogen is its disposition to burn in oxygen. These gases 
may be mixed in any proportion, and they will not act on 
each other at ordinary temperature ; but if a jet of hydro- 
gen issuing into oxygen or air be touched with a flame it 



68 INORGANIC CHEMISTRY. 

takes fire and burns, producing great heat but very little 
light, the flame being barely visible. The result of the 
combination of hydrogen and oxygen is water, as may 
be readily shown by holding a. glass tube over the flame, 
when moisture rapidly deposits on the side of the tube. 

Since hydrogen is inflammable and burns in the air it 
might be expected that it would not support the combus- 
tion of bodies which burn in oxygen. This may be proven 
by inserting a lighted taper into an inverted jar filled with 
hydrogen. The flame of the taper will be extinguished 
and the hydrogen will take fire and burn at the mouth of 
the jar. 

If a mixture of oxygen and hydrogen in certain propor- 
tion be raised to the temperature of ignition, which can be 
done by an electric spark or a flame, chemical union at 
once follows, attended by violent explosion. This property 
of the gases makes great care necessary in experimenting 
with a mixture of them. 

Weight for weight, hydrogen produces more heat in 
burning than any other substance. One pound of the gas 
in burning to water produces 34,200 units of heat. The 
explosion of the mixture of hydrogen and oxygen is of 
course due to the high temperature which results from the 
great heat of the chemical union, the heat expanding 
greatly the water vapor formed by the combination. The 
most violent explosion occurs when the gases are mixed in 
the proportion of two volumes of hydrogen to one of 
oxygen, a fact shown by the formula for water. If air be 
used instead of oxygen the explosion will be less violent, 
due to the presence of the inactive nitrogen. 

Owing to its tendency to combine with oxygen when 
heated, hydrogen will take oxygen from many other bodies 
containing it. This removal of oxygen is designated as a 
reducing or deoxidizing process, and the body accomplish- 
ing it is called a reducing or deoxidizing agent. Thus 



NON-METALS. 



69 



most of the metallic oxides are reduced at a red heat by 
hydrogen, which is one of the best reducing agents ; for 
example, CuO -f- H 2 = Cu -\- H 2 0. On the other hand a body 
which gives oxygen to another body is called an oxidizing 
agent. 

Preparation of Hydrogen. The process by which hydro- 
gen is usually prepared for laboratory purposes is to act 
upon dilute sulphuric acid with zinc. The zinc decomposes 
the acid with liberation of hydrogen and formation of zinc 
sulphate, as indicated by the following equation : 

Zn + H 2 S0 4 = ZnS0 4 + H 2 . 

For this purpose the zinc is cut into small strips, or 
granulated by pouring melted zinc into water from a 
moderate height ; a greater surface is thus exposed for 

contact with the acid. If 
the sulphuric acid is too 
strong, the zinc sulphate 
formed does not readily dis- 
solve off the zinc and the 
chemical action is retarded 
or stopped. On the other 
hand if the zinc be pure, it 
will scarcely act upon the 
acid ; the action is gener- 
ally facilitated by lead or 
other metal impurities which 
have an electrical effect not 
yet described. 

This method of preparing 
hydrogen can be adopted 
using common YVoullf bot- 
tles, shown in Fig. 3. The 
zinc is put into the bottle and the acid added through the 
funnel ; the hydrogen is passed out at the tube C and col- 




Fig. 3. 



70 INORGANIC CHEMISTRY, 

lected by displacement, or as described under oxygen. 
Hydrochloric acid may be used to replace the sulphuric in 
this process, or iron may be used instead of the zinc, but 
the hydrogen from iron is generally less pure than that 
from zinc. 

Hydrogen may also be prepared by passing steam over 
iron turnings contained in a tube heated to redness. The 
oxygen of the steam combines with the iron and the hydro- 
gen passes on through the tube, 3Fe + 4H 2 = Fe 3 4 -f- 4H 2 . 

It will be observed that the physical properties of hydro- 
gen place it with the non-metals while the chemical proper- 
ties ally it to the metals. Its chemical properties are so 
distinctly metallic that it is now sometimes classed and 
described with the metallic group. 

NITROGEN. 

Xitrogen occurs free in the atmosphere of which it con- 
stitutes about four-fifths, oxygen constituting nearly the 
whole of the remaining one-fifth. It also occurs in vol- 
canic gases, in the atmosphere of the sun, and in certain 
nebula?, and has been found in meteorites. In the com- 
bined form it exists as nitrous and nitric acids, in the com- 
pounds of ammonia, and in the organisms of plants and 
animals. 

Nitrogen was discovered by Rutherford of Edinburgh 
in 1772. 

Physical Properties. Xitrogen is a colorless, transparent, 
odorless, and tasteless gas. Water at 60° F. dissolves less 
than .015 its volume. By great cold and pressure it has 
been liquefied and solidified. 

Chemical Properties. In its chemical deportment nitro- 
gen is very inert. It combines directly with only a few 
elements, among which may be mentioned silicon, boron, 
magnesium, carbon, oxygen, and hydrogen ; with the last 



NON-METALS. 71 

named it combines, when one or both elements are in the 
nascent state, to form ammonia (NH 3 ). 

It has no positively poisonous properties, but is inca- 
pable of supporting respiration or combustion, oxygen 
being essential to these processes. 

Its presence in the atmosphere moderates the action of 
pure oxygen.* 

The slight affinity existing between nitrogen and the 
other elements gives a characteristic property to its com- 
pounds, many of which are very unstable ; thus the nitro- 
genized principles of plants and animals are prone to de- 
composition and many artificial compounds of nitrogen are 
highly explosive. 

Preparation of Nitrogen. Mtrogen is generally obtained 
in small quantity by burning phosphorus in air confined 
over water. A porcelain capsule containing phosphorus is 
floated on the water, the phosphorus is ignited and the 
whole covered with a bell-jar. The burning phosphorus 
unites with the oxygen, forming phosphoric oxide (P 2 5 ), 
which after a time is absorbed by the water. 

In larger quantity it may be prepared by passing air 
over finely divided copper heated to redness in a porcelain 
tube. The oxygen is removed by the copper. 

One of the easiest methods of preparing pure nitrogen is to heat in a 
glass retort potassium nitrite and ammonium chloride, KN0 3 -I- NH 4 C1 
= KC1 + 2H 2 + N a . 

ATMOSPHERIC AIR. 

The gaseous envelope surrounding the earth consists 

essentially of a mixture of nitrogen, oxygen, and argon, 

together with small but variable quantities of carbon diox 

ide (C0 2 ) and water vapor, with traces of other substances 

due to accidental or local causes ; among the latter may be 

mentioned ammonia (NH 3 ), marsh-gas (CH 4 \ sulphuretted 

* Raleigh has shown that nitrogen is combustible in air at a sufficiently 
high temperature. 



72 INORGANIC CHEMISTRY. 

hydrogen (SH 2 ), and sulphur dioxide (S0 2 ). The last two 
may generally be detected near cities and towns. Argon 
has been only recently discovered and constitutes about 
one per cent, of the atmosphere. The thickness of the 
earth' s envelope is estimated to be about forty-five miles, 
measured from the earth's surface. The air probably ex- 
tends beyond this height, but is in an extremely rarefied 
condition. 

Physical Properties. Due to its weight the atmosphere 
exerts a pressure on all bodies. The assumed average 
pressure of the atmosphere at the sea-level has been gener- 
ally adopted by engineers as the unit of pressure, and this 
unit is named an atmosphere. The pressure is generally 
expressed in terms of the barometric column, that is, the 
height of the mercury column which the air will support. 

In British measure an atmosphere is equivalent to the 
pressure of 29.905 inches of the barometer at 32° F. at Lon- 
don, and is very approximately 14.73 pounds on the square 
inch of surface. 

Essential Composition of the Atmosphere. We owe to 
Cavendish (1781) the first accurate determination of the 
proportions of the more important constituents of the at- 
mosphere (N and O). The presence of argon in the air was 
established in 1894. In dry air, freed from carbon dioxide, 
the constituents by volume are very approximately 21# of 
oxygen, slightly over 78$ of nitrogen, and slightly under 
1$ of argon. The oxygen is 23$ by weight. There is per- 
ceptible but little variation in these proportions, whatever 
the source of the air. For general purposes we may con- 
sider the atmosphere to contain four volumes of nitrogen 
to one of oxygen. 

Liquefaction of Atmospheric Air. This operation is now 
constructed upon a commercial scale, the result being 
accomplished by the cold resulting from expansion under 
great pressure. Liquid air is very mobile and has a bluish 



96 NON-METALS. 73 

divided copper contained in a glass tube, carefully weighed, 
and heated to redness; the nitrogen is made to pass into an 
exhausted globe. The increase in weight of the tube gives 
the weight of the oxygen, and of the globe the nitrogen. 

The two other most important constituents of the air are 
water vapor and carbon dioxide; these vary with condi* 
tions: About one per cent of argon is also present. 

Carbon Dioxide of the Air. The amount of carbon dioxide 
in the air varies slightly with the locality and with the 
season, being greater nearer centres of population than in 
the country, and greater in winter than in summer. In the 
country a greater amount has been found in the air at night 
than during the day, the difference being due to the differ- 
ent action of plants during the day and night; this diurnal 
variation is not observed at sea. 

The amount of carbon dioxide in normal air is from 
three to four volumes in ten thousand. In cities in winter, 
and especially in heavy fogs which prevent diffusion, it 
may rise to six or seven volumes in ten thousand. The 
amount of carbon dioxide, though relatively very small is 
actually very great. 

Upon this gas the vegetable kingdom is dependent for 
its existence; plants by the aid of sunlight decompose the 
carbon dioxide, retaining the carbon and returning the 
oxygen to the air. On the other hand, all animal respira- 
tion and all ordinary combustion take oxygen from the air 
and return to it carbon dioxide. Owing to this cyclic 
process the change in the proportion of these constituents 
in the atmosphere must be very slow. 

The quantity of aqueous vapor in the air is far less 
constant than the carbon dioxide. This quantity varies 
primarily with the temperature of the air, as already ex- 
plained in the subject of heat. The other important cir- 
cumstances which affect the quantity are the prevailing 
direction of the winds, the configuration of the land, and 



74 INORGANIC CHEMISTRY. 

the nearness of bodies of water. Upon the average the 
aqueous vapor is from 1 to 1.5 volumes to 100 of air. 

Other Gaseous Constituents of the Air. Ozone can nearly always be 
detected in normal air, and its presence is more common in the purer air. 
Hydrogen dioxide is also very generally present in the air ; its chemical 
actions are in many cases analogous to those of ozone, and it is difficult to 
distinguish between the two. Ammonia, or, more generally, its carbonate, 
is nearly always present in minute but variable quantity in the air. 
The ammonia results from the decomposition of organic matter, and in 
the presence of moisture, combines with the carbon dioxide and other acids 
present in the air; the nitrates and nitrites of ammonium are sometimes, 
from this source, present in the atmosphere. 

Other gases occur locally in minute quantities in the air, the most com- 
mon of which have been already mentioned, as sulphuretted hydrogen, 
sulphur dioxide, and marsh-gas. 

The new element, argon, is present in the atmosphere in small quantity. 
During last year (1898) there was reported another gaseous element of the 
atmosphere, called by its discoverer (C. F. Brush) etherion. 

Solid Constituents of the Air. In addition to its gaseous 
constituents, minute particles of solid matter are suspended 
in the air and generally termed dust. Atmospheric dust is 
made up both of inorganic and organic matter. The in 
organic matter is composed of various mineral compounds. 
The organisms are the propagators of mould, mildew, 
fermentation, and putrefaction, and it is probable that 
some of them are the agencies through which certain 
diseases are spread. 

COMPOUNDS OF HYDROGEN AND OXYGEN. 

WATER. 

Water is the most important compound of hydrogen 
and oxygen. With the exception of the air no substance 
is so indispensably necessary to terrestrial life as water. 
Its distribution is only second to that of the air, and its 
absolute amount is enormously greater. Water is the 



NON-METALS. 75 

cause of many of the most striking physical phenomena in 
nature, and its uses for economical and domestic purposes 
are innumerable. Besides the enormous quantities which 
are spread over the surface of the earth and distributed as 
vapor through the air, it is an important constituent of all 
living beings and of many minerals. 

The composition of water was discovered by Cavendish 
in 1781. 

Physical Properties of Water. Many of the physical 
properties of water are well known ; a few will be men- 
tioned here. Thick layers of water have a blue color. 
Water has greatest density at 4° C. or 39.4° F. In freezing 
water expands by .09 of its volume, so that eleven volumes 
of water become twelve volumes of ice. The melting-point 
of ice under constant pressure is constant (0° C. == 32° F.), 
but water may be cooled below this point and still remain 
liquid. 

Water evaporates at all temperatures, and ice at tem- 
peratures below 0° C. will give off vapor without melting. 
The absolute boiling-point of water or the temperature 
above which it cannot exist as a liquid is about 1076° F. 
(580° C). As already stated, water at maximum density is 
taken as the standard for the specific gravities of bodies in 
general, and it is also the standard for the specific heats of 
bodies in general. One volume of water at the boiling- 
point and under the standard pressure yields 1696 volumes 
of vapor at the same temperature and pressure, the specific 
gravity of the vapor being 0.622 (air — 1). 

Solvent Power of Water. This power of water is not 
thoroughly understood. It may be defined as the power of 
water to form a homogeneous liquid with another sub- 
stance brought into it. Thus many substances, gases, 
liquids, or solids, brought into water disappear and a 
homogeneous liquid results. The results of these actions 
are such that the constituents cannot be separated by 



76 rs'OBGAXIC CHEMISTRY. 

purely mechanical means. The substance thus mingled 
with the liquid is said to be dissolved by it or in solution 
in the water. As already stated, these solutions differ from 
mere mechanical mixtures, and also to a certain extent 
from true chemical compounds. 

If a very small amount of the substance be dissolved in 
the water the solution is said to be dilute ; when a large 
amount is dissolved it is a concentrated solution : and when 
the water will dissolve no more of the substance it is a 
saturated solution. There is no limit to the extent to 
which every solution may be diluted, but in the case of 
gases, solids, and of most liquids there is a limit to the 
amount of the substance that may be brought into solution ; 
but some liquids dissolve each other in all proportions — for 
example, water and alcohol. 

Solution of Solids. The quantity of a solid required to 
produce saturation generally varies with the temperature, 
most solids being more soluble in hot than in cold water. 
If a saturated solution of such a substance be made in hot 
water and then the water be allowed to cool it will, in 
general, not be able to hold so much of the solid in solution 
and the excess separates, or, as it is usually called, is de- 
posited in the solid form, often as crystals. 

The hot saturated solutions of some bodies do not deposit 
any of the dissolved substance if the solution is perfectly 
quiet while cooling and excluded from the air ; such solu- 
tions are called supersaturated. 

Water of Hydration. Many salts in crystallizing from 
their aqueous solutions retain in combination a greater or 
less amount of water, called water of hydration, which 
it retains with greater or less tenacity. The amount of 
this water varies with the conditions of crystallization, but 
the water and the salt are always present in molecular 
proportions by weight. Some salts when exposed to dry 
air lose their water of hvdration and crumble to a dry 



NON-METALS. 77 

powder ; this process is termed efflorescence. Those salts 
which do not part with their water of hydration in dry 
air at ordinary temperature do so at the boiling-temperature 
or at a somewhat higher one. 

Salts generally lose their color as well as their crystal- 
line form by the removal of their water of hydration. 
Some sympathetic inks owe their use to this property of 
changing color. A solution of the salt is used as ink, but 
is invisible until the paper used for the writing is warmed ; 
cobalt chloride is such an ink. 

Some salts retain a portion of their combined water, 
usually one molecule, more tenaciously than the remainder ; 
this is sometimes called ivater of constitution. In some cases 
it can be replaced by a salt. 

From the investigations of Guthrie it seems probable that all soluble 
salts form compounds with water at some temperature. Those salts which 
combine with water and are solid only at temperatures below 0° C. are 
called cryo-hydrates. 

Many salts which solidify without combined water may 
enclose some water mechanically ; such salts when heated 
are likely to fly to pieces with a small report and are said 
to decrepitate. Bodies which absorb moisture from the 
air and become damp and ultimately liquid are said to 
deliquesce. 

The thermal effect of the solution of a solid when there 
is no chemical action is cold. 

Solution of Liquids. Water dissolves many liquids, some 
in all proportions. In such event it is usual to say that 
the liquids mix in all proportions, though the solution may 
be accompanied by a decided chemical action with a de- 
velopment of heat ; water and sulphuric acid are examples. 
In other cases the solution is confined to certain limiting 
proportions of the liquids. In case of the solution o( solids 
and liquids a contraction takes place in the volume of the 



78 INORGANIC CHEMISTRY. 

solution, the volume being less than the sum of the volumes 
of the two bodies. 

Solution of Gases. Gases are very generally soluble in 
water to a greater or less extent, and the thermal effect of 
such solution is opposite to that in the case of solids, heat 
being produced. The heat is very evident when the gas is 
very soluble, as in the case of ammonia and hydrochloric 
acid. Gases in most cases are removed from solution by 
heating ; when not thus liberated they form definite com- 
pounds with the liquid and distil over with it. The com- 
pounds of hydrogen with chlorine and bromine are examples 
of this last class of gases. From the facts stated in regard 
to solutions it will be observed that, like alloys, they differ 
both from what we have defined as true chemical com- 
pounds and also from mere mechanical mixtures ; per- 
haps the most evident distinction is that they differ 
from true chemical compounds by having no invariable 
composition, and from mechanical mixtures by the fact 
that, except in a few cases, there is a limit to the propor- 
tions in which the constituents may be present. 

Chemical Properties of Water. It has already been stated 
that oxygen and hydrogen combining to form water 
develoj) great heat ; we should therefore expect water to 
be a permanent and stable compound. Although this is a 
fact, water can be readily decomposed in several ways. 

The alkali and alkaline-earth metals decompose water 
at the ordinary temperature ; for example, 

K 2 + H 2 = K a O + H 2 . 

Some other metals do so at higher temperature. It may 
also be decomposed by the electric current. At high tem- 
perature water is decomposed into its elements, the decom- 
position, according to Deville, beginning about 1000° C. and 
continuing with the increase of temperature up to about 
2500° C, Avhen it is completed. After the decomposition 



NON-METALS. 79 

has commenced any fall of temperature will cause a recom- 
bination of the elements. 

This general decomposition of a substance with increas- 
ing temperature, accompanied by a disposition of the con- 
stituents to combine and reproduce the substance by a 
reduction of temperature, is called heat dissociation, to 
which further reference will be made in Chapter III. 

In its action on vegetable colors, water is neither acid 
nor basic. It combines with both basic and acid oxides to 
form definite chemical compounds. Its combinations with 
the oxides of the alkali and alkaline-earth metals develop 
much heat and result in the compounds called hydroxides ; 
for example, 

K 2 + H 2 = 2KOH, CaO + H 2 = Ca0 2 H 2 . 

As already stated, it is not believed that water as such 
exists in these compounds, but the oxygen and the hydro- 
gen are present in the form of hydroxyl. 

Water combines with the acid oxides to form acids ; for 
example, 

H 2 + S0 3 = H 2 S0 4 . 

Composition of Water. The composition of water may be 
determined by analysis or by synthesis. The analysis or 
separation of water into its constituents may be accom- 
plished by passing an electric current through it under 
proper conditions. With proper arrangements the con- 
stituent gases may be collected and their volumes and 
weights determined. 

The composition by synthesis can be determined by 
causing oxygen and hydrogen to combine directly, as by 
the passage of the electric spark through a mixture of the 
gases under such conditions as give the volumes of the 
gases involved. From the volumes the weights can be 
computed from the relations of the specific gravities. 



80 INOBQANIC CHEMISTRY. 

The synthetic determination can be more accurately 
made by causing an unknown quantity of hydrogen to 
combine with a precisely determined weight of oxygen and 
then weighing the water produced. The difference between 
the weight of the water produced and the weight of oxygen 
employed gives the weight of hydrogen that has combined 
with the oxygen. This is designated as gravimetric syn- 
thesis. A convenient method often pursued is to pass 
pure dry hydrogen over a known weight of heated copper 
oxide and accurately weighing the water produced ; the 
loss of weight in the copper oxide gives the weight of the 
oxygen ; the difference between this and the weight of the 
water produced gives the hydrogen : 

CuO + H 2 = H 2 + Cu. 



NATURAL WATERS. 

Pure water is seldom or never found in nature. The 
impurities result from the materials, solids, liquids, or 
gases, with which it comes in contact, and they may be 
either in suspension or in solution. Suspended impurities 
are merely finely divided particles of matter mechanically 
distributed in the water, and they may be gotten rid of by 
subsidence or filtration ; water often contains no suspended 
matter. Soluble impurities must be separated by distilla- 
tion or a combination of this with more purely chemical 
means. 

The natural waters may be classified according to their 
occurrence as rain, sea, river, spring, and well waters. 

Rain Water. Rain is the purest form of natural water, 
but even it contains gaseous and dust particles derived 
from the atmosphere through which it passes. The gases 
dissolved by falling rain are of course those present in 
the atmosphere. Rain water accordingly always contains 



NON-METALS. 81 

oxygen and nitrogen ; generally more or less ammonia 
and carbon dioxide, and often traces of other gases, the 
quantity depending upon local conditions. 

By boiling rain or other natural water the gases in 
solution are driven out and may be collected. It is thus 
found that the oxygen and nitrogen in solution in these 
waters are not in the same proportion as they exist in the 
air. This is one of the best proofs that air is a mixture of 
oxygen and nitrogen and not a chemical compound. 

Spring and Well Water. The rain and the water result- 
ing from the melting of snow, sleet, and hail flow over the 
surface of the earth on their way to the sea. When these 
waters sink below the surface and reappear, they constitute 
springs ; if their subterranean channels be tapped artifici- 
ally we have wells. Spring and well waters, in addition to 
the impurities of rain water, dissolve many soluble sub- 
stances encountered in their flow ; the impurities in such 
water depending upon the rock material through which 
they pass. 

The most common and abundant impurities are the car- 
bonates of calcium and magnesium, the sulphates of cal- 
cium, magnesium, and sodium, the chloride of sodium, 
silica (silicon oxide), carbon dioxide, and hydrogen sul- 
phide. 

Many other substances of less frequent occurrence and of 
less importance are found naturally in these waters. 

By contamination from artificial sources, as by city or town sewage, 
etc., spring and well, and even river waters may become very impure and 
entirely unfit for human consumption. It is believed that zymotic diseases 
generally, and it is known that two of them, cholera and typhoid fever, are 
frequently propagated by drinking water. The infectious or zymotic matter 
is contained in the discharges of affected people and passes by defective 
drainage into sources of water supply. In cases of artificial contamination 
the additional impurities in the water are usually salts of nitrous and nitric 
acids, ammonia, and chlorides. By chemical analysis and a consideration 
of the sources of a water supply, its safety for drinking purposes can gen- 



82 INORGANIC CHEMISTRY. 

erally be determined, but any water contaminated by sewage should be 
classified as dangerous. 

Hard and Soft "Water. Common waters have been roughly 
classified as hard and soft, a classification originally depend- 
ing upon their action npon soap. Soap when rubbed in 
soft water forms a lather much quicker then when hard 
water is used. With the latter white, curdy flakes, not 
observed with the soft water, make their appearance before 
a lather is formed ; this action is due to chemical causes 
and will be presently explained. 

The hardness of water is mainly due to the presence in 
the water of the carbonates and sulphates of calcium and 
magnesium. The carbonates of the metals, except those of 
the alkalies, are not soluble in pure water, but if the water 
contains carbon dioxide in solution, as natural waters 
generally do, they will dissolve the carbonates. 

Magnesium sulphate is readily soluble in water and cal- 
cium sulphate very slightly so. 

The hardness due to the carbonates in solution is termed 
temporary, because it can be readily removed ; that due to 
the sulphates is called permanent, because of the difficulty 
of removing it. 

Since the temporary hardness brought about by the car- 
bonates in solution is due to the presence of carbon dioxide, 
if this be removed the carbonates will be precipitated. The 
carbon dioxide may be driven off by boiling, on account of 
its decreased solubility with increase of temperature, and 
the carbonates will deposit on the sides of the containing 
vessel. 

Calcium sulphate is very slightly soluble in cold water 
and less soluble at high temperature. By evaporation of 
the water and increase of temperature there would also be 
deposited some calcium sulphate, but the calcium sulphate 
can not be entirely removed by boiling alone. 

Similar depositions explain the furring of kettles and 



NON-METALS. 83 

incrustations of boilers. The deposits are usually colored 
brown or red, due to the presence of iron oxide and vege- 
table matter, the former resulting from the iron carbonate 
deposited from the water. 

The temporary hardness of the water may also be 
removed by adding to the water a solution of calcium 
hydroxide, which combines with the free carbon dioxide, 
removing it as calcium carbonate and causing the deposi- 
tion of the dissolved carbonate : 

H 2 + CaC0 3 + C0 2 + Ca0 2 H 2 = 2CaC0 3 + 2H 2 0. 

This is the principle of the Clark process for softening 
water. 

Both the temporary and the permanent hardness are removed by the 
household process of adding an alkaline carbonate to the waters : 

2Na a C0 3 + H 2 + CaC0 3 + C0 2 + CaS0 4 = Na 2 S0 4 + 2NaHC0 3 + 2CaC0 3 . 

But this is practicable only on a small scale. 

It is often desirable to prevent the incrustations in 
boilers, and the most efficient means yet suggested is to 
add ammonium chloride to the waters employed ; there are 
then formed ammonium carbonate and calcium chloride ; 
the latter remains in solution in the water, and the former 
volatilizes in the steam : 

2NH 4 C1 + CaC0 3 = (NH 4 ) 2 C0 3 + CaCl 2 . 

The incrustations formed in boilers fed with sea water 
are mainly due to calcium sulphate and magnesium hydrox- 
ide, the latter resulting from the magnesium chloride in the 
water. 

Natural Deposits from Hard Water. The metallic carbonates 
except those of the alkalies are insoluble or nearly so in 
pure water, but they dissolve in water containing carbon 
dioxide, and the greater the amount of carbon dioxide the 
greater the amount of the carbonates dissolved. 



84 INORGANIC CHEMISTRY. ~ 

Subterranean waters are often heavily charged with car- 
bon dioxide, and coming in contact with limestone rocks 
they dissolve much calcium carbonate. When these waters 
come to the surface of the earth the carbon dioxide escapes, 
due to diminished pressure, aud the dissolved carbonates 
are deposited. 

This explains the phenomena observed at the so-called 
petrifying springs, which are constantly depositing lime- 
stone, and will rapidly cover with it any body placed in 
their waters. This phenomenon is abundantly witnessed 
in the Yellowstone Park ; the objects are merely coated 
and not petrified. 

Such waters trickling into caves often deposit their 
salts so as to form large columns, often of great beauty, 
called stalactites and stalagmites. 

Of course when waters containing salts in solution are 
evaporated, they leave their salts behind, so that deposits 
may occur by evaporation of the water as well as by the 
removal of the carbon dioxide. 

It is possible that the solution of the carbonates generally by carbon 
dioxide in solution may be due to the formation of acid carbonates of the 
metals, but the formation of these substances has not been proved; and if 
they are formed, they are easily decomposed, for, as we have seen, boiling 
drives off the carbon dioxide ; if this is the case, the soluble carbonate of 
calcium is represented thus: 

CaC0 3 + CO, + H 2 = CaH 2 (C0 3 ) 2 . 
Action on Soap. To understand the action of hard water 
on soap it is necessary to know that soap is itself a metallic 
salt of an alkali metal and a fatty acid. Common soap may 
be represented by the formula NaFt, in which Ft stands 
for the complex formula of the fatty acid radical. When 
these soaps are treated with hard waters, the calcium and 
magnesium salts, by double decomposition, form the soaps 
of these metals, which are insoluble and perceptible as curdy 
scum on the water. A true lather from the soap will not 



NON-METALS. 85 

form until the salts to which the hardness is due are 
removed by the formation of these insoluble soaps. The 
action is indicated in the equation 

2NaFt + CaC0 3 = CaFt 2 + Na 2 C0 3 . 

River and Sea Waters. River water does not differ essen- 
tially from well and spring water, the natural quantity 
of both mineral and organic impurities being diminished 
by the conditions of continual motion and exposure to the 
air. 

Sea water contains the same salts as spring and river 
.waters, and in addition a large amount of common salt, 
about four fifths of the saline constituents of sea water 
being sodium chloride. The compounds of bromine and 
iodine are also found in small quantities in sea water. A 
gallon of sea-water usually contains about 2500 grains of 
mineral salts. Sea water has no point of maximum density 
• above the freezing-point and solidifies at — 2° C. 

Mineral Waters. Natural mineral waters are those spring 
waters which contain mineral substances in such quantity 
as to exert a medicinal effect on the animal system, or as 
to render them entirely unfit for drinking purposes. Min- 
eral and medicinal springs are very widely distributed ; 
some of the common kinds are chalybeate springs, which 
contain some salt of iron in solution ; saline springs, which 
contain one or more of a large number of mineral salts ; 
carbonated springs, which contain carbon dioxide in solu- 
tion ; hepatic or sulphur springs, which contain hydrogen 
sulphide in solution. The escape of the gaseous constitu- 
ents often produces effervescence ; the same spring often 
contains both solid and gaseous constituents. 

Purification of Water. Waters often become purer by 
natural processes. This is the case with running waters, 
and especially when they are subjected to thorough agita- 
tion and exposure to the air ; an unfit water may thus. 



86 INORGANIC CHEMISTRY. 

in a purely natural manner, become fit for drinking. The 
purity of all turbid water is greatly increased by allowing 
it to stand in tanks or reservoirs, by which most of the 
suspended matter is deposited. After remaining for some 
time in storage reservoirs it is customary to filter all large 
water supplies. The most common method adopted is to 
allow the water to flow through layers of sand of different 
degrees of coarseness. Sand filtration when properly 
carried on is very efficient in removing all suspended im- 
purities, but it has little influence on the dissolved matter. 
It is also claimed by Professors Koch and Frankland that 
sand filtration removes a very large per cent of microscopic 
organisms. Besides sand, filters of charcoal or of coke 
and sand have been employed for purification on a large 
scale. 

The Hyatt filter, which is largely used in this country, 
has coke and sand ; in this process a little alum is added 
to the water before filtration. 

Filters of finely divided iron have been used in Antwerp in case of 
very impure water ; these filters exert a chemical as well as a mechanical 
effect upon the water. There are many other methods of purifying 
drinking water on a small scale. For refined chemical purposes water is 
purified by distillation. 

Alum is frequently used to clarify water ; the effect is probably mainly 
due to the fact that if there be any carbonates in solution in the water 
the alumina is precipitated, which has a coagulating effect and carries 
suspended matter with it. 

HYDROGEN PEROXIDE, H 2 2 . 

This substance has the composition H 2 2 . It was discovered in 1818. 
IX is a great oxidizing agent in the case of many substances, readily giving 
up half its oxygen and being converted into water ; upon certain other 
substances it acts as a reducing agent, being itself converted into water 
and oxygen liberated ; it thus acts upon silver oxide : 

Ag 2 + H 2 2 = Ag 2 + 2 + H 2 0. 

Hydrogen peroxide, is a colorless, transparent, sirupy liquid : it is 



NON-METALS. 87 

heavier than water, has a bitter taste, and mingles with water in all 
proportions. 

Its most useful applications in the arts are by virtue of its oxidizing 
power. 

Paintings which have blackened due to the formation of lead sulphide 
can be restored to their original color by washing with a dilute solution of 
hydrogen peroxide, the lead being converted into lead sulphate. It is very 
important to the student of chemical philosophy because of its chemical 
relations. 

CARBON. 

Carbon occurs free in nature in three distinct allotropic 
forms, as diamond, graphite, and mineral coal. These 
three forms differ widely in appearance and physical prop- 
erties, but their chemical relations prove their identity. 
The first two are crystallized and very nearly pure carbon ; 
the third is amorphous, uncrystallized, and includes many 
varieties of coal, differing greatly in purity ; the three 
principal varieties are anthracite or hard coal, bituminous 
or soft coal, and lignite or brown coal. 

In combination carbon is widely distributed. It exists 
in combination with oxygen in the carbon dioxide of the 
air, is present in all mineral carbonates, and is a constituent 
of all organic substances. It is the element by virtue of 
which all organic substances turn black when heated with 
limited access of air. All forms of carbon are solid, in- 
soluble in all ordinary solvents, fused iron being the only 
known solvent, non-volatile ( xcept at the high temperature 
of the electric arc. 

Diamond. This is one of the rarest of substances and one 
of the most precious gems. Before the discovery of the 
African mines the diamond was usually obtained from 
alluvial washings, and little was known of its origin. 
These mines, it is thought, have yielded more diamonds 
than all the previous production of the world. The dia- 



88 INORGANIC CHEMISTRY. 

mond has been prepared artificially. This was accom- 
plished in 1893 by Moisson, by dissolving carbon in molten 
iron at a high temperature and then cooling it rapidly. 
The largest specimens thus produced were about .5 mm. 
Diamond is the hardest substance known. 

If heated very highly out of contact with air, as by the 
electric arc, it is converted into a black mass resembliug 
graphite, but without loss of weight. It can be burned in 
the air and then leaves a small quantity of ash. 

Graphite. This is found in beds and veins in the oldest 
crystalline rocks, has a grayish-black color and metallic 
lustre, and is so soft as to leave a mark when rubbed on 
paper. 

It is a very useful substance, being employed in mak- 
ing the so-called lead pencils, for covering iron to prevent 
rust, and for mixing with clay to make crucibles which 
are designed to stand high and sudden changes of tempera- 
ture. Graphite is often produced artificially in the cooling 
of molten cast iron. It is also used as a reducing agent in 
some metallurgic operations. 

Graphite is now prepared artificially by highly heating 
a mixture of about 97 per cent of amorphous carbon 
and 3 per cent of iron oxide or silica in an electric 
furnace ; or the charge may consist of anthracite coal 
alone, in which case the graphite is left nearly free 
from impurity, the material which constitutes the ordi- 
nary ash being volatilized at the high temperature. This 
industry is now conducted on a large scale at Niagara 
Falls. 

AMORPHOUS CARBON. 

This term includes, in addition to the native mineral 
coals, all the common artificial forms of carbon. The min- 



NON-METALS. 89 

eral coals will be fully described in mineralogy. The prin- 
cipal artificial varieties of amorphous carbon are charcoal, 
lampblack, animal charcoal, and coke. Lampblack is the 
form of carbon which is often deposited upon cold objects 
by the flame of gas or burning oil. These combustible 
bodies are composed almost entirely of carbon and hydro- 
gen, and if the flame be cooled, or the supply of air limited, 
the carbon escapes combustion and is deposited in a finely 
divided state, commonly called soot. 

Lampblack is manufactured by subjecting organic sub- 
stances rich in carbon to imperfect combustion, that is, 
combustion with an insufficient supply of air. For this 
purpose oils, fats, resins, and tarry matters are burned 
with a limited supply of air and the products of combus- 
tion conducted through a flue into a large chamber, along 
the sides and from the ceiling of which are suspended 
large cloths upon which the unburned carbon is deposited. 
The lampblack thus obtained usually contains resinous or 
oily substances and other impurities depending upon the 
organic body burned. It is, however, sufficiently pure for 
the purposes for which it is generally used, viz., printer's 
ink and black pigments. 

Charcoal. Charcoal is the form of carbon obtained by 
heating wood out of contact with air. If wood be heated 
in the air, it is entirely consumed except a small quantity 
of ash, which is composed of the incombustible mineral 
matter of the wood. The part that has disappeared, the 
sap and the woody fibre, are composed almost entirely of 
carbon, hydrogen, and oxygen. The woody fibre (cellulose), 
which constitutes nearly the entire solid part of the wood, 
is more than one half carbon, the remainder being oxygen 
and hydrogen. 

If wood be heated to redness out of contact with the air, 
no combustion can occur, but under this temperature the 
constituent elements of the wood rearrange themselves into 



90 



INORGANIC CHEMISTRY, 



simpler and more stable compounds. In this change the 
carbon is mainly left, retaining the form of the wood, but 
largely diminished in volume and still more so in weight. 

This resolution of a complex substance into simpler and 
more stable forms under the influence of high temperature 
out of contact with air is termed destructive distillation. 

In the case of wood it is often called charring, coaling, 
or carbonizing. 

The earliest and still the most common way of preparing 
charcoal for fuel is as follows. 

Preparation of Charcoal. Billets of wood are built into 
a mound or stock around an upright pole or bundle of brush- 
wood, which is withdrawn after the stock is completed 
and leaves an opening called the chimney (Fig. 4). The 




Fig. 4. 

billets may be nearly vertical, or horizontal, or inclined at 
any angle. When completed the mound usually has a 
dome shape, and may have a diameter varying from thirty 
to fifty feet and with a height from ten to fifteen feet. The 
finished heap is covered with chips, leaves, soil, and earth, 
and often the coal dust of a previous burning is used for 
this purpose. Numerous openings are left around the 
base of the mound for the admission of air and escape of 
the products of distillation. 

The kiln is kindled in the centre, and after the fire is 



NON-METALS. 91 

started the top is closed. More air is required in the early 
stages of the carbonization, so that the openings at the 
bottom are gradually closed and the mound is left to 
smoulder and cool. By this process the weight of charcoal 
obtained never exceeds 25$ of the weight of wood used. 
In this country, as in many other places, kilns or charcoal- 
ovens are often built of brick or masonry ; they are gener- 
ally rectangular with arched tops, or of a beehive shape. 
In these ovens the destructive distillation is accomplished 
by the combustion of a certain portion of the wood of the 
heap. In America there is claimed for such ovens an 
economy of time and a gain in the quantity and quality of 
the charcoal, but these advantages are denied at other 
places. The ovens are sometimes arranged to collect the 
products of distillation. 

Charcoal is also made by the destructive distillation of 
the wood in cast iron retorts, the wood being placed in a 
perforated iron case within the retort. In this method the 
heat is obtained from other fuel than the wood itself, 
though sometimes the combustible products from the wood 
are led to and burned in the furnace beneath the retort. 
At other times these products are condensed and used in 
the preparation of acetic acid, wood-naphtha, and methyl 
alcohol. 

Distillation in retorts yields a greater per cent of char- 
coal and of better quality than the methods first described. 

All forms of carbon thus obtained contain impurities 
due to the non-combustible and non-volatile mineral matter 
of the wood. 

Properties and Uses of Charcoal. Charcoal, under 
ordinary conditions, is one of the most unchanging solids 
known. This property of carbon has long been recognized, 
and is shown in the charring of wood intended to withstand 
extended exposure. Oak staves planted in the bed of the 
Thames by the ancient Britons in their defensive works 



92 INORGANIC CHEMISTRY. 

against Csesar were charred, and thus have been perfectly 
preserved to the present day. Charred stakes for marking 
the limiting lines of estates are often used. 

Charcoal is very porous and, due to this property, exerts 
an absorbent action on many substances. Oxygen is ab- 
sorbed by it in considerable quantity and many other gases 
to a far greater degree. This is especially noticeable with 
those gases which can be readily liquefied. It absorbs 
under ordinary conditions fifty times its volume of hy- 
drogen sulphide and twice that amount of ammonia. A 
gas thus absorbed, if capable of oxidation, will be acted 
upon by the oxygen also contained in the charcoal. This 
property of charcoal explains its frequent use in deodorizing 
offensive matter and in purifying offensive atmosphere. 

Ammonia and hydrogen sulphide are two of the most 
common products of putrefaction, and both are readily 
absorbed by charcoal. 

The absorbing power of charcoal also extends to liquids 
and solids ; it is accordingly used to make water-filters. 

Water passed through a good charcoal filter is clear and 
odorless. It is especially efficient in removing coloring 
matter. The charcoal has to be periodically heated to 
retain its absorbent powers. 

Besides the above uses charcoal is largely employed as 
a fuel and in the manufacture of gunpowder. 

With a free supply of air it burns readily without 
flame, producing carbon dioxide and yielding about twice 
as much available heat as an equal weight of wood. One 
pound of carbon burned to carbon dioxide will produce 
8080 units of heat, C. scale. Its use in the manufacture of 
gunpowder will be referred to under that subject. 

Animal Charcoal. This form of carbon is made by the 
destructive distillation of animal substances such as bone, 
skin, blood, etc. ; commonly from the first named substance. 
Bones are composed approximately of one third animal 



NON-METALS. 93 

matter and two thirds mineral matter, three fourths of this 
mineral matter being calcium phosphate. The animal mat- 
ter is composed mainly of carbon, hydrogen, oxygen, and 
nitrogen. The result of the destructive distillation of 
bones is a charred mass consisting of about one tenth carbon 
and nine tenths mineral matter. 

The decolorizing power of this form of charcoal far 
exceeds that of other forms, and it has frequent technical 
application for this purpose and is used industrially in 
sugar refineries and distilleries. 

The products from the distillation of bones are often 
collected and used, and the mineral matter from the bone- 
black itself is eventually employed as a fertilizer. 

Coke. Common coke results from the destructive dis- 
tillation of soft or bituminous coal. This distillation is 
sometimes made by burning coal in heaps, as in the conver- 
sion of wood into charcoal, but generally the coke is 
prepared in specially constructed ovens, and of these there 
are many forms. They are constructed of suitable masonry 
lined with fire brick. In some of these the heat for the 
distillation is obtained by burning part of the coal in the 
oven ; in others the heat is obtained without burning any 
of the coal in the oven. In the latter kind the combustible 
gases driven from the coke and other fuel are burned to 
supply heat. The forms of coke ovens are too numerous 
for description here; the object in all cases is to accomplish 
the distillation with as little consumption of fuel as pos- 
sible. 

The ovens are also varied in construction, depending 
upon whether they are arranged to secure the tar and am- 
monia. In this country the coke is usually made in bee- 
hive ovens and the secondary products are not then saved, 
though a few recent American plants have adopted ovens 
to prevent this great waste. In Europe the retort-ovens 
are very generally employed, and, in certain localities, the 



94 INORGANIC CHEMISTRY. 

by-products from the volatile constituents of the coal equal 
in value the coke produced. The coke contains, in addition 
to the fixed carbon, the incombustible ash of the coal. 

Coke is of a dark gray color with a slightly graphitic 
lustre ; it produces a much higher temperature than com- 
mon coal, and is much used in iron-smelting and other 
metallurgic operations. 

Coke is always produced in the manufacture of coal-gas, 
the coal in the operation being distilled in closed retorts. In 
this manipulation it often happens that some of the denser 
gases containing carbon and hydrogen, driven from the coal, 
are decomposed by the high temperature and the carbon de- 
posited upon the sides of the retort ; this deposit is known 
as gas-coke. It is used for plates in certain forms of electric 
batteries and also for the manufacture of carbon rods for 
electric arc-lights. 

Chemical Properties of Carbon. Carbon at the ordinary 
temperature is an inactive element, not combining with any 
other element ; at higher temperature it combines directly 
with sulphur, hydrogen, and oxygen, and under proper con- 
ditions will combine with other elements ; at elevated tem- 
perature it is especially active in combining with oxygen. 
Heated to redness it burns brilliantly in pure oxygen, and by 
the aid of heat it abstracts oxygen from many oxides, remov- 
ing and combining with the whole or a part of their oxygen. 

When burned with a full supply of air carbon always 
yields carbon dioxide ; with a limited supply carbon 
monoxide is produced. In case an oxide gives up its 
oxygen at a low temperature to carbon, carbon dioxide 
is generally formed ; but if at a high temperature carbon 
monoxide is produced. These actions are represented by 
the accompanying equations : 

2CuO + C = 2Cu + C0 2 ; 2ZnO + 2C = 2Zn + 2CO. 

This removal of oxygen from a body has already been 



NON-METALS. 95 

defined as a reduction ; hence carbon is a reducing agent. 
It is the most important reducing agent employed in the 
industrial arts, and upon this property and its heat-giving 
power depend its uses in metallurgic operations. 

COMPOUNDS OF CARBON AND OXYGEN. 

CARBON DIOXIDE. 

There are known two compounds of carbon and oxygen, 
carbon monoxide and carbon dioxide, both of which are 
gaseous at ordinary temperature. The latter is the more 
important ; it has already been stated that it is a constitu- 
ent of the atmosphere, being normally present in the 
proportion of from three to four volumes in ten thousand of 
the air. Its constant occurrence in the air is readily under- 
stood from known considerations. 

It is the product of the combustion of any form of car- 
bon or any compound of carbon in a full supply of air. As 
all common fuels are composed mainly of carbon or its com- 
pounds, it may be said that carbon dioxide is an abundant 
product of all ordinary combustion. 

It is likewise given off in all animal respiration, the ox- 
ygen of the air, which is inspired, combining with the car- 
bon of the system to form carbon dioxide, which is exhaled. 

All living vegetation extracts carbon dioxide from the air ; 
but when the plant dies, the process of decomposition, in the 
course of time, restores the carbon dioxide to the air again. 
If the plant is devoured by animals or consumed for fuel, 
its carbon eventually returns to the air as carbon dioxide. 

Carbon dioxide is also given off to the air during the 
processes of fermentation and putrefaction of organic sub- 
stances. 

It is present to a greater or less extent in all spring- 
waters, and in some places, especially in volcanic regions, it 
escapes rapidly from such waters when they come to the 
surface, giving effervescing springs. It often issues in 



96 INORGANIC CHEMISTRY. 

considerable quantity from openings in the earth's crust. 
When coming from such openings, or even from springs, it 
sometimes accumulates in neighboring depressions in such 
quantity as to destroy the life of animals venturing into 
them. Such a poison depression has been found at the east 
side of the Yellowstone Park ; the poison valley of Java is 
another. The accumulation of gas around the soda springs, 
so called, in southeastern Idaho often causes the death of 
birds seeking water. 

The air which permeates soils is found to be richer in 
carbon dioxide than is atmospheric air. 

In the combined form it occurs as a constituent of all 
limestones and other carbonates, and consequently exists 
in this form in enormous quantity. Calcium carbonate 
constitutes over 96 per cent of oyster- and egg-shells. 

Physical Properties of Carbon Dioxide. Carbon dioxide at 
ordinary temperature is a colorless gas and has a slightly 
acid taste and smell. Its formula shows it to be much 
heavier than air, and its greater density explains its dis- 
position to seek the lower levels. At 14° C. water dissolves 
its own volume of carbon dioxide, and the quantity dis- 
solved is directly proportional to the pressure to which 
the gas is subjected. When the pressure is diminished or 
removed the amount dissolved is diminished, and if there 
is much diminution of pressure the gas escapes with effer- 
vescence. 

Carbon dioxide can be liquefied without very great difficulty to a mobile 
colorless liquid which will not mix with water. Its boiling-point in the 
liquid state is — 88° C. Much of the liquid carbon dioxide is now manu- 
factured for use as a fire extinguisher. By causing it to evaporate under 
an air-pump its temperature is lowered to — 130° C. Like many other 
bodies which are liquefied by great pressure its coefficient of expansion is 
very great, being greater than the coefficient for gases. 

Chemical Properties of Carbon Dioxide. Carbon dioxide is 
not combustible, as it cannot take up more oxygen. If 



NON-METALS. 97 

will not support ordinary combustion and will extinguish 
flame ; a few bodies which have a great affinity for oxygen 
will burn in carbon dioxide. If potassium be ignited and 
then dipped into a jar of carbon dioxide it will continue to 
burn. Air which contains a little less than 3 per cent by 
volume of carbon dioxide will extinguish a taper, that is, 
when the carbon dioxide is about one eighth the volume of 
the oxygen. Carbon dioxide is not poisonous when taken 
into the stomach, but it will not support respiration. It is 
not poisonous in this case, but merely suffocates by de- 
priving of the necessary amount of oxygen, and also pre- 
vents the escape of the carbon dioxide from the system. 

A taper burning in a confined space is extinguished as 
soon as the carbon dioxide reaches a certain amount and 
long before all the oxygen is exhausted. Similarly, con- 
fined air becomes unfit to breathe long before the oxygen 
is exhausted. Any considerable amount of carbon dioxide 
above the normal in air to be respired is objectionable, in 
that it diminishes the proportion of oxygen. The actual 
amount of pure carbon dioxide that must be present in the 
air to render it unfit for respiration is not definitely settled. 
It has been found that air containing as much as 5 per cent 
may be breathed without injury, and recent experiments in- 
dicate that a much larger proportion of pure carbon dioxide 
may be breathed for several hours without ill effect. 

It has been shown that the bad effects experienced in 
poorly ventilated rooms are due to waste products other 
than carbon dioxide, given off from the lungs during 
respiration. Besides the carbon dioxide, water vapor, 
nitrogen, and oxygen of the expired air, there are other 
organic substances undergoing decomposition which have 
a poisonous action on the system, and to these are to be 
largely attributed the unwholesome conditions so rapidly 
developed in overcrowded and poorly ventilated rooms. As 
carbon dioxide is constantly given off in respiration along 



98 INORGANIC CHEMISTRY. 

with other organic impurities, the amount of the first in 
the air will indicate approximately the quantity of the 
latter, and therefore may be taken as a test of the fitness 
of the air for respiration. 

Generally speaking it may be stated that when the 
volume of the carbon dioxide is over y^- the volume of 
the air it should not be breathed for any considerable time ; 
when the volume of carbon dioxide reaches -^ the vol- 
ume of the air its effects soon become perceptible in languor 
and disagreeable sensations, and any amount above this 
is very deleterious ; when the amount has reached three 
per cent it has been known to produce death, 

A well, fermenting tun, or any confined space where 
this gas is suspected should be tested before entering it. 
If a candle-flame is made dim by the air, the space should 
be considered unsafe. When any person is quickly over- 
come by such an atmosphere another person cannot safely 
go to the rescue without first increasing the proportion of 
oxygen to the carbon dioxide. This may often be quickly 
done by moving an open umbrella, a bundle of straw or 
of brush up and down through the space 

The above described properties of carbon dioxide make 
evident the necessity for good ventilation. The amount of 
carbon dioxide given off from the lungs and skin of an adult 
amounts to about -^ cubic feet per hour ; an ordinary three- 
foot gas-burner gives off about two and one half times that 
amount. In order that the added carbon dioxide shall be 
distributed through the proper amount of air to fit it for 
respiration, it is evident that a large amount of fresh air 
must be introduced into constantly occupied rooms. It is 
of course easy to compute this amount under any given 
conditions. In general it may be stated that perfect ven- 
tilation should be prepared to supply one thousand cubic 
feet of air per man per hour, though one half that amount 
is usually considered good ventilation. 



NON-METALS. 



99 




Fig. 5. 



Preparation of Carbon Dioxide. Carbon dioxide is in- 
variably produced when carbon is burned in a full sup- 
ply of oxygen ; for example, 
C + 2 = C0 2 ; from this 
source it always contains 
other substances. 

It is readily prepared for 
laboratory purposes by act- 
ing upon fragments of marble 
(CaC0 3 ) with dilute hydro- 
chloric acid. The carbon diox- 
ide escapes with effervescence 
and is usually collected by 
upward displacement, being 
somewhat soluble in water. 
The apparatus described for 
^making hydrogen may be 
used in this case. The or- 
dinary manner of collecting the gas for illustrations is 
shown in Fig. 5. The action is represented thus : 

CaC0 3 + 2HC1 = CaCl 2 + H 2 + C0 2 . 

Any of the other mineral acids will liberate carbon 
dioxide from a carbonate, so that it can be readily pre- 
pared in many ways. 

Carbon dioxide is largely used in the manufacture of 
artificial mineral waters. 

Carbonic Acid and its Salts. An aqueous solution of car- 
bon dioxide exhibits weak acid properties. It colors blue 
litmus red, but the blue color returns upon drying. The 
solution acts upon bases and forms the salts called carbon- 
ates. The formula? of the carbonates indicate the existence 
of an acid having the formula H 2 C0 3 , though this substance 
has not been isolated. It is probable that the acid is 
formed whenever carbon dioxide is passed into an aqueous 



• « 



100 INORGANIC CHEMISTRY. 

solution, but it readily breaks up into carbon dioxide and 
water. On account of the similarity of the carbonates to 
other salts, they are universally considered as formed by 
the replacement of hydrogen in carbonic acid by metals, 
and the acid is bibasic. 

The carbonates are a very important class of bodies, and 
it may be well to repeat their properties. The carbonates 
are all decomposed by mineral acids, are all, with unim- 
portant exceptions, insoluble in water, except the carbon- 
ates of the alkalies, and are all decomposed by heat except 
those of the alkalies. They are all soluble in water contain- 
ing carbon dioxide in solution. 

CARBON MONOXIDE. 

Physical Properties. Carbon monoxide is a colorless, 
tasteless gas with a very faint smell; it is slightly lighter 
than air, as may be seen from its formula. It is almost in- 
soluble in water. Its critical temperature is about — 140° C. 

Chemical Properties. Carbon monoxide is an extremely 
poisonous gas. It acts upon the red corpuscles of the blood 
and deprives the blood of its power of distributing oxygen 
to the system. It forms an explosive mixture with one half 
its volume of oxygen. It burns in air with a pale blue 
flame, producing carbon dioxide, but extinguishes ordinary 
flame. At high temperature it readily takes oxygen and 
forms carbon dioxide ; for this reason it is a powerful 
reducing agent, removing oxygen from many metallic oxides 
and reducing them to the metallic state. It is accordingly 
a very valuable agent in many metallurgic operations. Its 
union with oxygen gives out much heat ; carbon monoxide 
burning to carbon dioxide gives more than two thirds of all 
the heat produced by the complete combustion of the 
carbon to carbon dioxide. 

Production and Uses. Carbon monoxide is always pro- 
duced by the incomplete combustion of carbon or carbona- 



NON-METALS. 101 

ceous substances, that is, when these are burned with an 
incomplete supply of air. 

If carbon dioxide be passed over heated charcoal or 
other carbon it gives up one half its oxygen to the carbon, 
both being converted into carbon monoxide, as indicated 
by the equation 

C0 2 + C = 2CO. 

This action explains the phenomenon frequently observed 
in connection with an open anthracite coal fire, when a pale 
blue flame is seen to play over the top of the mass of coal : 
the combustion of the coal in the lower part of the grate 
with full supply of oxygen produces carbon dioxide ; this, 
passing through the heated layers of coal above, is con- 
verted into carbon monoxide. This carbon monoxide upon 
reaching the upper surface of the coal comes in contact 
with the air and burns with the blu^ flame observed. 

This ready production of carbon monoxide is often made 
use of in metallurgic operations when it is desired to have 
a flame play over the surface of an ore placed on the hearth 
of a reverberatory furnace. 

Anthracite coal, which burns with but little flame, is 
frequently employed in such furnaces, and it then becomes 
necessary to heap the coal in the grate so as to form a mass 
of considerable height. The carbon monoxide is produced 
precisely as described above in the grate and passes into 
the furnace chamber, and when air is admitted the carbon 
monoxide burns with a flame. By properly regulating the 
supply of air a high temperature can be produced. 

The attraction which carbon monoxide has for oxygen 
at a high temperature enables it to remove this element 
from many of its compounds. Carbon monoxide is accord- 
ingly one of the most powerful reducing agents, and, as 
will be subsequently seen, the property is generally turned 
to account in removing oxygen from the metallic oxides, 
reducing the oxides of the metals. 



102 INORGANIC CHEMISTRY. 

Carbon monoxide is one of the essential elements of 
water-gas, hydrogen being the other ; carbon dioxide and 
nitrogen are also present in limited quantities. This water- 
gas is now largely used for illuminating and other pur- 
poses. 

Water-gas is prepared by passing steam over white-hot 
coke ; the result is indicated by the equation 

C + H 2 = CO + H 2 . 

Some carbon dioxide is also present, for the reason that 
at lower temperature the action of steam on carbon is to 
produce carbon dioxide. 

For laboratory purposes carbon monoxide is readily obtained by heating 
potassium ferrocyanide with dilute sulphuric acid. 

COMPOUNDS OF CARBON AND HYDROGEN. 

Carbon and hydrogen form a larger number of com- 
pounds than any other two elements. These compounds 
are designated as hydrocarbons. They enter largely into 
the composition of nearly all combustible bodies, and in- 
clude many of the inflammable gases, naphtha, benzene, 
etc. 

It is probable that all hydrocarbons are primarily de- 
rived from the organic kingdom, and the study of these 
compounds belongs to organic chemistry. Only three of 
the simple hydrocarbons will be mentioned here; they are 
all constituents of common coal-gas. 

METHANE ; MAKSH-GAS ; CH 4 . 

Methane is the only hydrocarbon containing one atom 
of carbon. It is found abundantly in the free state in na- 
ture. It is frequently termed marsh-gas from its occurrence 
in marshy places. The bubbles of gas which rise to the sur- 
face when the mud at the bottom of stagnant pools is dis- 
turbed are generally marsh-gas. It is believed to be one of 



NON-METALS. 103 

the products of the decomposition of vegetable matter dur- 
ing its conversion into coal; hence its frequent occurrence 
in coal-mines, where it is known as fire-damp. It is proba- 
ble that all the hydrocarbons of petroleum, and similar oils, 
are derived in the same way. 

Physical and Chemical Properties. Methane is a colorless, 
odorless, and tasteless gas. Its formula shows it to be 
much lighter than air, hence it diffuses and mixes rapidly 
with air. When mixed with oxygen or air in suitable pro- 
portions it explodes violently upon ignition. The most 
violent explosion is indicated by the equation CH 4 + 4 = 
C0 2 -f- 2H 2 0, in which there is just enough oxygen to com- 
pletely oxidize the carbon and hydrogen. The relative 
volumes of marsh-gas and oxygen for this action are shown 
in the equation to be two volumes of oxygen to one of 
marsh-gas; it would accordingly require ten volumes of air 
for the complete oxidation of one volume of marsh-gas. 

It is marsh-gas which so frequently gives rise to the 
fatal explosions in coal-mines. It will be observed that the 
products of the explosion are also irrespirable and consti- 
tute the after -damp of mine explosions. 

Marsh-gas has not been prepared by the direct union of 
its elements, but can be prepared artificially. Marsh-gas 
does not unite with other bodies without decomposition ; 
chlorine decomposes it in direct sunlight, atoms of chlorine 
successively replacing atoms of hydrogen. At a high tem- 
perature marsh-gas is separated into carbon and hydrogen. 

ACETYLENE ; ETHINE ; C 2 H 2 . 

Acetylene can be produced directly from its elements by 
highly heating carbon in an atmosphere of hydrogen. This 
may be accomplished by immersing the electrodes of a 
voltaic arc in an atmosphere of hydrogen. The opera- 
tion is of but little practical importance, but it is of greal 
theoretical interest because it is the first step in the 



104 INORGANIC CHEMISTRY. 

artificial production of a large number of organic com- 
pounds. 

Physical and Chemical Properties. Acetylene is a colorless 
gas having a faint odor of geranium. From an ordinary 
gas-jet it burns with a smoky flame, but when the air and 
gas are properly apportioned its flame is brilliantly lumi- 
nous. It inflames spontaneously when brought into contact 
with chlorine, and when mingled with air gives a mixture 
that can be exploded by ignition. 

Preparation of Acetylene. Acetylene is now prepared on 
a large scale by heating lime with powdered coal or other 
carbon in an electric furnace, by which calcium carbide is 
prepared. The calcium carbide if immersed in water 
yields lime and acetylene by this reaction : 

CaC 2 + H 2 = CaO + C 2 H 2 . 

This method of preparing acetylene promises to give it 
a brilliant future as an illuminant, for which purpose it is 
admirably adapted because of its great light-giving power 
in proportion to the heat and objectionable products result- 
ing from combustion. Many forms of acetylene producers 
or generators have been put upon the market. They are 
generally arranged to operate automatically, the gas being 
liberated as required. 

OLEFIANT GAS; ETHYLENE; C 2 H 4 . 

defiant gas like the other two hydrocarbons just de- 
scribed is a product of the destructive distillation of coal. 
It may be obtained artificially by the action of sulphuric 
acid upon alcohol. It is a colorless gas with a somewhat 
ethereal odor. It burns with a luminous flame, and for 
complete combustion one volume of the gas requires three 
volumes of oxygen : 

C 2 H 4 + 6 = 2C0 2 + 2H 2 0. 



NON-METALS. 105 

The mixture of olefiant gas and oxygen in this propor- 
tion explodes with violence when ignited. 

The gas unites with chlorine and bromine, forming oily 
liquids ; hence the term olefiant (oil-making). This action 
may be applied to determine the amount of ethylene in 
coal-gas. 

When subjected to high temperature olefiant gas is 
decomposed with a deposit of carbon and a separation of 
hydrogen, marsh-gas, and acetylene. 

COMBUSTION AND FLAME. 

Combustion. The hydrocarbons above described, either 
separately or together, are found in many of our common 
inflammable gases; combustion and the properties of flame 
are accordingly very naturally taken up here. 

Combustion in general may be defined as chemical 
action accompanied by heat and light. The term combus- 
tion ordinarily applies to the chemical combination of the 
oxygen of the air with the body burned. 

The temperature to which a body must be raised in 
order that combustion may take place is called the igniting 
point. 

When a body is said to be combustible, it is generally 
meant that it will burn in air. It is also customary to 
regard one of the bodies taking part in the action as the 
combustible, and the other as the supporter of the combus- 
tion. The enveloping medium is usually taken as the sup- 
porter of combustion, and the other as the combustible, so 
that in the ordinary cases air is the supporter of combus- 
tion. These limitations are without scientific basis, and the 
supporter of combustion may be any medium in which the 
phenomenon will occur. 

The process with proper arrangements is reversible, 
when both the bodies taking part in the combustion are 



106 INORGANIC CHEMISTRY. 

gases, so that the supporter of combustion may become the 
combustible and the reverse ; thus while we usually burn 
hydrogen in oxygen, oxygen may be burned in hydrogen. 
Similarly air may be burned in coal-gas and the reverse. 

Flame. When both substances taking part in the com- 
bustion are gases, the action results in flame, which may 
be defined as gaseous matter heated to a temperature at 
which it becomes visible. Solids which do not volatilize 
at the temperature of combustion do not ordinarily give 
flame ; carbon and iron are familiar examples. 

Luminosity of Flame. This may be due either to the 
incandescence of gaseous matter, or of solid particles 
present in the flame. A high temperature is always essen- 
tial to incandescence and consequently to luminosity. In 
all ordinary flames the gaseous matter which is heated re- 
sults from the flame-gases themselves ; the solid matter 
may result from these gases or may consist of foreign 
matter introduced for the purpose. 

It has been found as a general rule that denser gases 
and vapors when heated give off light at lower temperature 
than the less dense, and heated solids emit light at lower 
temperatures than gases. 

Luminosity without Solid Particles. Examples of 
combustible bodies which afford dense flames and bright 
light without solid particles are seen in the case of phos- 
phorus, arsenic, and carbon disulphide, which, when 
burned in oxygen, produce highly luminous flames, though 
all the products of combustion are gases at the tempera- 
ture. The luminosity of the flame does not depend entirely 
upon the vapor density of the constituent gases them- 
selves, but is affected by the pressure to which these gases 
are subjected. 

The luminosity of flame may often be increased by in- 
creasing the pressure of the medium surrounding the flame. 

Thus the flame of carbon monoxide burning in oxygen 



NON-METALS. 107 

at ordinary pressure is only moderately luminous, but may 
be greatly increased by doubling the pressure. The faintly 
luminous flame of hydrogen burning in oxygen may be 
greatly brightened by increasing the pressure of the oxy- 
gen. For this reason a candle burns more brightly at a 
low than a high elevation. 

Flame Containing Solid Matter. The light -giving 
power of many of the common illuminating gases is still 
further increased by the presence of solid matter intention- 
ally introduced into the flame, or separated from the flame- 
gases during the chemical action of combustion. The 
Welsbach burner, among common gas-burners, is an illus- 
tration of free foreign solid matter introduced into the 
flame. The great luminosity in this burner is due to the 
introduction into the flame of a gauze hood of certain in- 
fusible metallic oxides. 

Tn the candle, oil-lamp, simple gas flames, and common 
flames generally, the light is mainly produced by the in- 
candescence of solid carbon particles which are separated 
in a finely divided state from the flame-gases. There are 
also usually present or produced in these flames dense hy- 
drocarbons which emit light. The influence of such solid 
particles may be illustrated by blowing powdered charcoal 
across a hydrogen flame. 

The calcium or lime-light owes its luminosity to a frag- 
ment of lime very highly heated by the oxyhydrogen 
flame. 

It is seen from the above considerations that the most 
essential conditions for luminosity in a flame are : (1) high 
temperature and vapors which are of themselves dense or 
made dense under the conditions of burning; (2) highly 
heated solid particles. The influences of these conditions 
operate simultaneously in most common illuminating 
flames. 

Structure of Flame. The simple flame is one that re- 



108 INORGANIC CHEMISTBY. 

suits from the combustion of a substance that undergoes 
no decomposition, but combines directly with the sup- 
porter of the combustion ; hydrogen and carbon monoxide 
burning in oxygen are illustrations. There is but a single 
product of combustion in such cases. All such flames 
when the gas issues from a circular jet consist of a conical 
sheath of flame surrounding a cone of the gas. The flame- 
cone is hollow, that is to say, the interior cone of the gas 
is not burning. This fact may be simply proved by quickly 
depressing a white sheet of paper into the flame, when the 
flame- cone will char an annular space, while the interior 
circle will be unaffected. A live match may be suspended 
in the inner cone without ignition if not allowed to touch 
the sides of the flame-cone. The conical shape of the flame 
is due to the fact that the gas issues from the jet in the 
form of a cylinder and, being under a little greater pres- 
sure than the air, assumes the form of a slightly diverging 
cone. 

The gas first issuing from the jet burns as a ring around 
the orifice; the next layer of gas must pass above this ring 
in order to reach the air for its combustion. Each succes- 
sive ring must pass through the preceding to reach the air; 
and as each burning ring diminishes the volume of un- 
burned gas, these rings must grow smaller, and the con- 
verging cone is the only possible form. This explanation 
holds for the shape of the candle-flame or other flame re- 
sulting from the issuance of gas from a cylindrical 
wick. 

Hydrocarbon Flames. It has already been stated that 
these bodies enter largely into the composition of all our 
common illuminating oils and gases. They undergo de- 
composition during combustion, and the products of com- 
bustion are produced at successive stages. They give rise 
to flames more complex in structure than those just de- 
scribed. The common flames under this head are those of 



NON-METALS. 109 

gas, oil, and the candle; the last will be described as typi- 
cal of all. 

In the first case the fuel is supplied at the burner in the 
gaseous state, the gas having been obtained from the de- 
structive distillation of coal at a distance ; in the second 
(oil) the fuel is liquid and is converted into gas at the lamp. 
In the candle the tallow or wax is solid, so that it must be 
melted and distilled during the operation of burning. 

Candle Flame. In the candle flame (Fig. 6) there are 
three concentric cones; the interior is dark, and is composed 
of unburned gas resulting from the destructive 
distillation of the tallow; the next, and the 
largest part of the flame, is brightly luminous, 
and the outer cone is thin and only faintly 
luminous. There is also a bright blue cup at 
the base of the cone. 

The flame-cone proper consists of the out- 
side and faintly luminous cone, the next or 
luminous one, and the blue cup at the base; 
the interior dark cone consists of combustible 
gases to which air does not penetrate, and is 
not part of the flame. In the luminous cone 
combustion is taking place, but the air-supply 
is not sufficient for complete combustion. At 
Fig. 6. ^e temperature of the cone there results a 
decomposition of some of the hydrocarbons with a separa- 
tion of free carbon. A portion of this carbon, heated to 
whiteness by the combustion of other portions, confers 
the luminosity upon this cone. In the outer cone, where 
the air supply is abundant, the remaining carbon together 
with the hydrogen is burned. 

The blue cup at the base is probably due to the perfect 
combustion of a thin layer of gas at that point and to the 
lower temperature due to the presence of an excess of air. 
The combustible gases of the inner cone may be readily 




110 INORGANIC CHEMISTRY. 

extracted and burned at some distance from the flame by 
inserting one end of an open glass tube, six or more inches 
long, into the cone. 

The unburned carbon in the luminous cone can be shown 
by depressing upon it a white porcelain plate. 

Flame for Special Purposes. Lighting Flames. From 
the foregoing considerations of the nature, properties, and 
structure of flames, it is evident that several considerations 
must enter into the construction of burners for different 
purposes. The Argand gas-burner is one of the most widely 
used burners for gas lighting. The gas in this burner issues 
from the annular space between two concentric cylinders. 
The gas flame is a hollow cylinder which is surrounded by 
the chimney, and air is supplied to the flame both from the 
inside and outside of the cylinder. The chimney acts ef- 
fectively in producing a draft, and thus giving a liberal 
supply of air, which, in combination with the regulated 
flow of gas, permits the proper adjustment of the two for 
the best light. If there be too great a proportion of the gas 
some of the carbon escapes unburned, and the flame smokes, 
and the temperature is not high enough to produce a brill- 
iant light. By using two chimneys and causing the air 
that feeds the flame to pass down between them, there is 
less chilling effect on the flame, and an equal light may be 
obtained with a less consumption of gas. The Argand 
burner may be converted into the Welsbach, already re- 
ferred to, by the insertion of a durable gauze mantle into 
the flame and regulating the air and gas supplies so as to 
produce the highest temperature. 

Smokeless Flames. Since luminous flames in general 
contain unburned carbon, they deposit soot when they 
come in contact with cooler solids. When bodies are to 
be heated by flame, as in laboratories and kitchens, it is 
therefore advantageous to have flames in which the com- 



NON-METALS. 



Ill 



bustion is as perfect as possible, producing a smokeless 
flame. 

This result is accomplished by mixing the air and gas 
in certain proportions before combustion, so that the 
hydrocarbons are burned without the separation of car- 
bon ; this also causes the disappearance of the luminous 
part of the flame. By a proper adjustment of the air and 
gas the flame from the combustion of a given amount of 
gas is smaller and the temperature higher. 

The principle upon which smokeless burners are con- 
structed is well shown in the Bun sen burner, Fig. 7. In its 

simplest form this burner con- 
sists of a cylindrical tube 
mounted on a substantial stand. 
The gas is led in at the base and 
ascends the tube, near the bot- 
tom of which there are two holes 
for the admission of air. The 
flow of the gas draws air into 
the tube, and the mixture is 
burned at the top of the tube. 
The holes for the admission of 
the air can be entirely or partly 
closed. By entirely closing the 
air holes the flame is white and 
luminous; by admitting the 
proper proportion of air the 
flame becomes smaller, of a blue color, and nearly non- 
luminous. This loss of color was formerly supposed to 
be almost entirely due to the complete combustion of 
the hydrocarbons without the separation of the carbon. 
It is now known that the effect can be brought about by 
admixture with the hydrocarbons of other gases than air, 
as nitrogen and carbon dioxide. The loss of luminosity 
in the case of air is due partly to the more perfect com- 




Figk7. 



112 INORGANIC CHEMISTRY. 

bustion, to the cooling effect of the nitrogen, and to the 
fact that in the presence of nitrogen a higher temperature 
is required to decompose the hydrocarbons. The cooling 
effect of the nitrogen prevents the separation of the car- 
bon at certain parts of the flame, but the more perfect 
combustion makes the temperature at other parts higher 
than the corresponding parts of the luminous flame. 

The flame of the ordinary Bunsen burner consists of 
only two cones. The inner cone is a mixture of air and 
gas; combustion is taking place only in the outer one. 
That the flame does not travel inward is due to the rate of 
motion of the mixed gases ; in the outer cone this speed is 
diminished so that the gases can be raised to the point of 
ignition. If the rate of flow of the gases be diminished, the 
flame will penetrate further and further inward and can be 
made to strike down the tube to the point of inflow of the 
gas and air. The absence of flame in the inner cone of the 
Bunsen burner may be shown in the manner already given 
for certain other flames. 

The Blowpipe Flame. This flame is produced by forc- 
ing a stream of air across a common gas, candle, or lamp 




Fig. 8. 
flame. The mouth blowpipe is an instrument of great 
utility. In its simplest form it consists of a bent tube 
terminating in a small end with an aperture. This flame, 
Fig. 8, shows three cones, but they are peculiar in appear- 
ance, being long and pointed. The innermost cone is com- 
posed of a mixture of air and combustible gases not in the 



NON-METALS. 113 

state of combustion ; the second cone is blue in color and 
consists of gases undergoing combustion, but with an in- 
sufficient supply of air ; the outer cone is but very faintly 
luminous, and the combustion is there complete. The 
space between the outer and innermost cone is filled with 
hot combustible matter which displays great reducing or 
deoxidizing power ; especially is this so at the point of the 
second cone ; this flame is accordingly called the reducing 
flame. Almost any metallic oxide placed just in the tip of 
this cone is deprived of its oxygen and reduced to the 
metallic state. 

The highly heated air just beyond the point of the outer 
cone oxidizes very readily; hence this outer cone is termed 
the oxidizing flame. In the mouth blowpipe it must be 
understood that the air is not propelled from the lungs, 
but simply from the mouth by the muscles of the cheek. 
The current of air may be produced by a bellows or other 
mechanical means. 

Oxyhydrogen Flame. By forcing a stream of pure 
oxygen through a gas flame, a blowpipe flame of very 
high temperature may be produced. A flame from a mix- 
ture of hydrogen and oxygen in proper proportions gives 
the highest temperature obtainable by purely chemical 
means. In the production of the oxyhydrogen flame, the 
gases (hydrogen and oxygen) are usually led by tubes 
from separate holders to the jet or blowpipe, where they 
are burned and allowed to mix only just before burning. 
Special precautions are made in the blowpipe so that the 
mixture cannot there explode. 

Safety Lamps. The temperature to which a gas must 
be raised in order that combustion may take place has 
already been defined as its ignition point, commonly 
called the kindling point. Combustion cannot take place 
until this temperature is reached, and if the temperature 
of the burning gas be reduced below this point the 



114 INORGANIC CHEMISTRY. 

flame will be extinguished. This fact may be simply 
illustrated with the candle flame by coiling a thin coppeT 
wire into a cylindrical spiral about half an inch long and 
of such diameter as to coincide with the flame cone. If 
the coil be placed over the candle, the flame will be ex- 
tinguished ; but if the coil be first heated and then placed 
over the flame, it will shoot above the coil and continue to 
burn. 

A copper wire gauze of sufficiently fine meshes may be 
placed over a gas-jet, and the flame will not extend above 
the gauze ; or if the gas be lighted above the gauze, the 
flame will not pass below. In each of these cases the tem- 
perature of the burning gases is reduced below the kindling 
point and combustion ceases. 

Different substances have different ignition points ; and 
owing to this fact a wire gauze through which a marsh-gas 
flame will not readily pass permits the passage of the 
hydrogen flame. 

The above considerations make clear the principles of 
safety lamps. The most celebrated of these is Davy's 
miner' s lamp. This is an oil lamp the flame of which is 
enclosed in a cage of wire gauze made double at the upper 
part, where the heat of the flame is most felt. The gauze 
has 400 or 500 meshes to the square inch. The lamp is so 
arranged that the reservoir can be supplied with oil and 
the wick trimmed without unscrewing the cage and thereby 
exposing the flame of the lamp. 

In an explosive atmosphere of marsh-gas and air the 
fire-damp may burn within the cage, but the flame will be 
extinguished by the gauze and not ignite the mixture out- 
side. 

The lamp thus serves to give indications of the state of 
the atmosphere in a mine, and enables an examination to 
be made without risk to the inspector. This is the true 



NON-METALS. 115 

use of the lamp, and it is not intended to enable workmen 
to labor in an explosive atmosphere. 

The explosions which have so often proved disastrously 
fatal in coal mines, and which the safety lamp is intended 
to help prevent, have in most cases been due to explosive 
mixtures of marsh-gas, other hydrocarbons, and hydrogen 
with the air. Fine coal dust in the air of the mine increases 
the liability to explosion, and in some cases this dust has 
been the sole cause of explosion. 

Explosions have occurred in flour mills through the 
general diffusion of flour dust throughout the building. 
Any readily combustible substance thickly distributed as 
fine dust through the air will burn with explosive effect. 

Slow and Flameless Combustion. There are several 
substances which possess the power of causing the slow 
combustion of certain gases. Finely divided platinum or 
even platinum foil will bring about the combination of 
hydrogen and oxygen. A clean thin strip of platinum foil 
put into a jar containing a mixture of hydrogen and oxy- 
gen will immediately cause their combination to begin, and 
if the foil be very thin its temperature may rise to redness 
and cause the explosion of the remaining mixture. 

If the platinum be reduced to the state of minute divi- 
sion, as is the case of platinum black, or its surface greatly 
extended, as in spongy platinum, it immediately becomes 
red-hot in a mixture of hydrogen and oxygen. Hydrogen 
falling upon platinum black in air is immediately ignited. 
Upon this principle lamps which light automatically have 
.been constructed. 

If a thin piece of platinum foil be heated, but not suffi- 
ciently to emit light, and held in a jet of gas escaping from 
a Bunsen burner, its temperature will rise to redness, and it 
will continue to glow as long as the mixed gases impinge 
upon it. This is a case of flameless combustion. The same 
result may be brought about in vapor of alcohol and ether. 



116 INORGANIC CHEMISTRY. 

Although platinum possesses this property to a marked 
degree, it is not limited to this metal; palladium and gold 
display it to a less degree, while glass and certain stones 
show it to a still lower degree. 

A full explanation cannot be given of these results, but 
they are due to the property which the solids possess of 
condensing gases upon their surfaces, or of absorbing them 
and bringing them under the temporarily changed condi^ 
tions within their sphere of mutual action. 

When the ignition point of a substance is lower than the 
temperature produced by its combustion, it will burn when 
once ignited; but when the reverse is the case there will be 
required a continual application of external heat to keep 
up the combustion. 

SILICON. 

In many of its chemical relations silicon resembles car- 
bon; but while the latter is the characteristic element of 
the organic kingdom, the former is one of the most abun- 
dant elements of the mineral world. 

Silicon is not known to occur in the uncombined state, 
but in combination it is, next to oxygen, the most abun' 
dant and widely distributed element. In combination with 
oxygen, as silicon dioxide (silica), it occurs in sand and the 
various forms of quartz, which are among the most common 
and abundant forms of natural minerals. It also exists 
very widely in the silicates which result from the combina- 
tion of silica with various metallic oxides. These silicates 
form the great mass of the rocks which make up the earth' s 
crust. Silicon oxide is also found in certain species of the 
vegetable kingdom. 

The element silicon is of no practical importance; it has been obtained 
both in the amorphous and crystalline forms, being in the first a dark 
brown powder, and in the second of a metallic lustre resembling graphite, 
The powder burns vividly in oxygen until covered by a coating of silica; 



NON-METALS. 117 

the graphitic form is incombustible. The amorphous form readily attacks 
platinum when heated with it. It is claimed by some that there is a third 
form of silicon corresponding to the diamond form of carbon. 

Preparation of Silicon. Silicon may be prepared by decomposing 
potassium silico-fluoride at high temperature by potassium, as indicated by 
the equation 

K 2 SiF 6 + K 4 = Si + 6KF. 
After cooling the potassium fluoride is dissolved out by water. 



The only oxide of silicon, silica (Si0 2 ), is a very impor- 
tant compound. Alone or in combination it forms a very 
large proportion of the earth' s crust. The purest natural 
form of silica is rock-crystal, a clear transparent- variety of 
quartz. The dense white varieties of sand are nearly pure 
silica ; in a less pure form silica and the silicates constitute 
the greater part of nearly all soils. Its action in soils seems 
to be mainly mechanical. Silica is found in the outer 
sheaths of certain grasses and reeds, and as tabasheer in the 
joints of the bamboo. This fact proves its solubility to a 
certain extent, otherwise it could not be taken up by plants. 
Many hot springs and geysers also dissolve it. It is depos- 
ited in large quantities by the springs and geysers of the 
Yellowstone Park. 

The natural varieties of silica are insoluble in pure 
water, but hot alkaline solutions readily dissolve the 
amorphous varieties, and under high temperature and pres- 
sure also dissolve many of the crystallized forms. 

Silica is essentially an acid oxide, forming salts with 
many metallic oxides. Owing to its non-volatility, it de- 
composes all salts of volatile acids when highly heated 
with them. It thus replaces acids which at a lower tem- 
perature displace it. When heated with bases, silica 
generally unites with them, forming silicates. The silicates 
are the most common and abundant of minerals. As feld- 



118 INORGANIC CHEMISTRY, 

spars and micas the silicates enter largely into the com- 
position of granitic rocks, and the different varieties of 
clay are hydrons silicates of aluminnm. Common glass is 
a mixture of several silicates. The silicates as a class are 
all insoluble except certain alkaline silicates in which there 
is a large proportion of the base. 

Silicic acid is generally represented as tetrabasic and 
the formula written H 4 Si0 4 , or Si0 2 with 2ILO, but the 
formulae of many of the silicates indicate their derivation 
from silica combined with more or less than two molecules 
of water. 

Silicon Carbide. This compound (SiC) is prepared by 
heating silica with carbon in an electrical furnace. It 
is popularly known as carborundum. Since 1896 it has 
been largely used as an abrasive, and very recently it has 
been successfully utilized to form a refractory coating 
over the fire-brick linings of furnaces. The entire product 
of this country is made at Niagara Falls. 

BORON. 

This element has not been found in the free state. In combination it is 
almost entirely confined to the mineral kingdom, though its presence has 
been detected in grape-vines and a few other plants. It is the basis of 
boric acid, in which combination it is found in certain volcanic waters and 
forming many borates of the metals, one of the most important and com- 
mon of which is sodium borate or tincal. 

The element may be obtained by heating boron trioxide with potassium: 

B 2 3 + 3K 2 = B 2 + 3K 2 0. 

In this manner boron is obtained as a dark brown powder. 

Boric Oxide and Acid. Boron forms but one oxide, the formula of 
-which is B 2 3 . This oxide forms three oxyacids. The native acid found 
in volcanic regions is tribasic, represented by the formula 3H 2 0, B 2 3 , or 
"H3BO3, but is converted into other forms by the action of heat; at red heat 
all the water is driven off. 

The acid is an antiseptic and is sometimes used alone or with glycerine 



NON-METALS. 119 

to preserve meats and other food. The solution of the acid in alcohol im- 
parts a green color to the flame of the vapor. It will give color to steam 
issuing from a boiling solution of the acid if a flame be held in the steam. 
Borates. At high temperature boric oxide combines with many metal 
lie oxides, giving glassy borates which often have characteristic colors; 
upon this property depends the main use of boric acid in the arts. The 
formulae of most of the borates do not indicate their derivation from a 
tribasic acid. Borax or sodium borate is one of the most important of this 
class of salts. Borax occurs native in tincal. It is readily prepared by 
the action of boric acid on sodium carbonate. It will be further mentioned 
under the compounds of sodium. 

COMPOUNDS OF HYDROGEN AND NITROGEN. 

Ammonia (NH 3 ). This is a compound of hydrogen and 
nitrogen, indicated by the formula N"H 3 . It is primarily 
of organic origin and results from the putrefaction of 
organic matter, from the destructive distillation of coal, 
bones, and other organic matter. It has been found in the 
emanations of volcanoes. It is constantly removed from 
the air through absorption by rain and by the soil. In the 
combined form it is frequently present in beds of guano 
(the excrement of sea- fowls), and as the chloride and sul- 
phate in certain volcanic regions. It is also present in small 
quantity as carbonate, nitrite, and nitrate in soils and 
water, where, in the two last named forms, it becomes 
available for plant food. 

Animals during life, and both plants and animals after 
death, return to the air in the form of ammonia the nitrogen 
which existed in their organisms, and possibly some of it is 
returned as free nitrogen. They thus return to the air the 
nitrogen which was taken from it. The manner in which 
the nitrogen of the air was originally made available for 
food and started upon its endless circuit has been difficult 
to determine and even now is not thoroughly understood. 
It has lately been found that certain species of bacteria 
exist which are capable of oxidizing the nitrogen of the air 



120 INORGANIC CHEMISTRY. 

and thus starting it upon the cycle of plant service. One 
form of these bacteria is found to ply its vocation in con- 
nection with the growth of leguminous plants, having its 
home in the roots of the plants. It is also found that bac- 
teria are instrumental in transforming the nitrogen of dead 
organic matter into available shape for plant use again. 

Physical Properties of Ammonia. Ammonia is a colorless 
gas, having a strong, pungent odor which excites to tears. 
It has a caustic, burning taste. Its specific gravity is eight 
and one half referred to hydrogen. It is liquefied by a 
temperature of — 33°.5 C. at atmospheric pressure, or by a 
pressure of six and one half atmospheres at 10° C. In the 
liquid state it is a colorless mobile liquid which at 0° C. 
has a specific gravity .62. Its boiling point is — 33°.5 C. 
under atmospheric pressure. 

During the evaporation of liquid ammonia great reduc- 
tion of temperature takes place, and it has for this reason 
been frequently used in the artificial production of cold for 
freezing and other purposes. 

Gaseous ammonia is more readily soluble than any 
other gas, water at 15° C. dissolving over seven hundred 
and fifty times its volume, the volume of the solution being 
something more than one and one half times that of the 
water. 

During the solution of the gas more heat is evolved 
than corresponds to the liquefaction of the gas, which can 
only be attributed to chemical action. The gas, however, 
can be entirely -removed from the water, and no definite 
compound of the two is known. The solubility of the gas 
increases as the temperature of the water diminishes. The 
great solubility of ammonia in water may be strikingly 
illustrated by filling a bottle with ammonia by displace- 
ment over mercury, making the mouth of the bottle air- 
tight and transferring to a vessel of water ; when the stop- 
per is removed the water immediately fills the bottle, and 



NON-METALS. 121 

if tlie water be admitted by a tube through the cork it will 
play as a fountain. 

In Carre' s freezing apparatus for ice, liquid ammonia is 
allowed to evaporate from a strong iron receiver which sur- 
rounds the water to be frozen. The vapor of the ammonia 
is absorbed by water contained in another receptacle, so as 
to increase the rapidity of evaporation from the receiver. 
The ammonia can then be driven out of the water in the 
second vessel by heat and condensed by its own pressure 
in the receiver, and the operation repeated. The boiler is 
of course allowed to cool before evaporation from the re- 
ceiver begins. 

Chemical Properties of Ammonia. Ammonia is alkaline to 
a very high degree ; it has the alkaline action on vegetable 
coloring matter and combines with acids, neutralizing them 
completely. It can be kindled in the air, but will not con- 
tinue to burn when the external source of heat is removed. 
In an atmosphere of pure oxygen the ammonia burns with 
a continuous name when lighted. 

It is decomposed into its elements by passage through 
a red-hot tube, two volumes of ammonia producing one 
volume of nitrogen and three volumes of hydrogen. Am- 
monia escaping into an atmosphere of dry chlorine takes 
fire and burns, producing ammonium chloride. 

Its solution is largely used in the arts and as a reagent 
in the chemical laboratory. By neutralizing the solution 
of ammonia with the mineral acids, salts are obtained bear- 
ing strong resemblance to the corresponding salts of sodium 
and potassium. This taken in connection with the other 
strong alkaline characters, gave rise to the suggestion that 
the solution of ammonia contains an alkaline hydroxide 
(NH 4 OH) similar to KOH and NaOH, in which NH 4 per- 
forms the same function as potassium and sodium. 

This hypothetical radical (NH 4 ) is called ammonium. 
The salts from the solution of ammonia may be considered 



122 INORGANIC CHEMISTRY. 

as formed either by the direct union of ammonia with the 
acids or by the replacement of the hydrogen of the acid by 
ammonium ; in the latter case ammonium acts similarly to 
the metals in forming salts. The salts of ammonium will 
be more fully described in connection with the metallic 
salts. Ammonia is easily expelled from its salts by heat- 
ing with slaked lime or a solution of potash or soda, On 
account of its striking odor this gives a ready test for such 
a salt. 

Preparation of Ammonia. There are many sources from 
which ammonia may be obtained, but the chief source is 
the ammoniacal liquor of the gas-works. The manufacture 
of gas will be described later ; at present it is sufficient to 
know that ammoniacal liquor results from the destructive 
distillation of coal in the manufacture of gas. This liquor 
contains several compounds of ammonia, two of the most 
important of which are the carbonate and hydrosulphide, 
(JN"H 4 ) 2 C0 3 and NH 4 HS. The liquor containing these sub- 
stances is heated with lime in a still ; the lime displaces the 
ammonia from combination, and it is conducted into a tank 
containing sulphuric or hydrochloric acid. The acid com- 
bines with the ammonia, forming ammonium sulphate or 
chloride, depending upon the acid used. There is always 
some hydrogen sulphide driven off in the operation, but 
this escapes from the receiving tank and is burned. 

The sulphate of ammonia is the form in which the 
ammonia is generally sold for fertilizing. The chloride 
after purification by heating and sublimation is employed 
for various purposes and is the form generally used to 
obtain pure ammonia. From the chloride, ammonia is 
readily obtained by heating it with powdered lime, as in- 
dicated by the equation 

21S T H 4 C1 + CaO = CaCl 2 + H 2 + 2NH 3 . 
The gas may be conducted into a vessel of water until a 



NON-METALS. 123 

solution of the required strength is obtained. By this 
means liquor ammonia is prepared as an article of com- 
merce. 

The most convenient way of obtaining ammonia for 
laboratory purposes is to gently heat liquor ammonia ; the 
gas passes from the solution very readily, and may be col- 
lected by downward displacement or over mercury. The 
gas for laboratory use may be prepared directly from the 
chloride as above indicated if the liquor ammonia be not on 
hand. 

In the above method of separating the ammonia from 
the ammoniacal liquor of the gas-works, the ammonia was 
displaced from its combination by another base, lime being 
used. It is possible to treat the ammoniacal liquor with an 
acid (sulphuric or hydrochloric) which combines with the 
ammonia and liberates carbon dioxide and hydrogen sul- 
phide; this is sometimes done. The sulphate or chloride 
thus produced is mixed with many other constituents of 
the liquid and is more difficult to purify. 

Other sources for the commercial preparation of ammo- 
nia are the blast-furnaces and coke-ovens; the ammonia in 
these cases also resulting from the destructive distillation 
of coal. 

Although the direct combination of nitrogen and hydro- 
gen is accomplished only with difficulty, this compound is 
sometimes produced when nitrogen is brought into contact 
with nascent hydrogen. 

Hydrazine or Hydrazoic Acid. There are two other compounds of 
nitrogen and hydrogen, viz.: hydrazine (N 2 H 4 ) and hydrazoic acid (N 3 H), 
but they have up to the present time received no useful application. 

COMPOUNDS OF NITROGEN AND OXYGEN. 

These elements under ordinary conditions show no dis- 
position to enter into combination; however, there are live 
distinct compounds of them known, viz., N 2 0, NO, N 2 8 , 



124 TNOBGANIG CHEMISTRY. 

NO, = N 2 4 , and N 2 5 , These formulae show that the 
quantities of oxygen that unite with a given quantity of 
nitrogen are to each other as 1 : 2 : 3 : 4 : 5. 

There are three oxyaeids of nitrogen corresponding to 

the first, third, and fifth of these oxides. 

The compositions of these acids and their relations to the correspond- 
ing oxides will be seen from the following formulae : 



s° 


Hyponitrous anhydride. 


So 


Hyponitrons acid 


^o 


Nitrous anhydride. 


S°o 


Nitrous acid. 


5S° 


Nitric anhydride. 


r° 


Nitric acid. 



The first two acids have not been obtained in a free or pure state but 
are known from their salts. 

The third is the most important of these acids and is the 
one from which all the compounds of nitrogen and oxygen 
are obtained directly or indirectly. 

HTTBIC ACID. 

Preparation. The combination of oxygen and nitrogen 
can be brought about directly by artificial means, and in 
the presence of water nitric acid results, but the acid is 
always prepared from natural nitrates. 

The manufacture of nitric acid is a commercial process 
and is accomplished by heating sodium nitrate with sul- 
phuric acid in suitable retorts, usually in cast-iron cylin- 
ders. 

The proportion of the reagents and the final reaction are 
indicated by the equation 

2XaX0 3 — H 2 S0 4 = Xa,S0 4 — 2HX0 3 . 

The nitric acid vapor produced is conducted from the re- 
torts into stoneware or other suitable receivers in which it 
is condensed, the receivers being cooled by water. During 






NON-METALS. 125 

the operation some of the vapor of the nitric acid is de- 
composed thus : 

2HN0 3 = H 2 + O + 2N0 2 , 

the last product being a red vapor which in the solution of 
the condensed acid gives it a yellowish-red color. 

Pure nitric acid is colorless, but if exposed to sunlight 
the above reaction takes place with the resulting color. 
The oxygen thus liberated exerts a pressure on the acid in 
the bottle and may result in ejecting some of the liquid 
when the stopper is withdrawn. The strongest acid in the 
commercial manufacture is obtained by using pure reagents 
and collecting the middle portion of the distillate separately. 
For the most concentrated, colorless acid, some other pre- 
cautions are necessary. The strength of the acid is indi- 
cated by the specific gravity: the strongest has the specific 
gravity 1.53; common aqua fortis has the specific gravity 
1.30 and contains less than 50 per cent of acid. 

On a small scale in the laboratory the acid may be made 
from either potassium nitrate or sodium nitrate by heating 
the salt with sulphuric acid in a glass retort and condens- 
ing the acid in a flask cooled by a wet cloth. In the lab- 
oratory method it is better to use the reagents in the 
proportions indicated by the following equation, 

KN0 3 + H 2 S0 4 == KHSO4 + HNO3 , 

for this reaction requires lower temperature and the acid 
salt is more easily dissolved out of the retort than would 
be the normal sulphate, which would be formed were 
double the amount of nitrate used. A given quantity of 
Chili saltpetre will produce more acid than the same weight 
of common nitre, as is evident from the formulae of the 
two nitrates. 

In India and other dry countries potassium nitrate oc- 
curs in certain places as an efflorescence on the surface of 



126 INORGANIC CHEMISTRY. 

the soil. This is the principal source of nitre. Sodium 
nitrate or Chilian saltpetre occurs as immense beds along 
the coast of northern Chili and southern Peru. 

Properties of Nitric Acid. Mtric acid when pure is a 
colorless liquid which fumes strongly in the air owing to 
condensation of the acid vapor by the aqueous vapor of 
the air. It has a very choking, suffocating smell. It is 
very corrosive ; the strongest acid produces painful sores 
when brought into contact with the skin, and the dilute 
acid turns the skin and other organic matter yellow. A 
drop of sulphuric or hydrochloric acid will stain cloth red, 
and the color may be partially or wholly restored by 
prompt application of ammonia, while the stain of nitric 
acid is intensified by ammonia though the corrosive action 
is prevented. 

Under ordinary conditions strong nitric acid is 
weakened and weak nitric acid strengthened by boiling, 
until an acid of 68 per cent is reached, when the whole dis- 
tils over without change. If the pressure under which 
the distillation occurs be varied the strength of the distil- 
Lite will also vary. 

Mtric acid is a powerful oxidizing agent, very few sub- 
stances being able to withstand its action. Phosphorus 
hopped into a dish containing strong nitric acid is oxid- 
ized, often with such energy as to give flame, P 2 5 being 
|3roduced. 

Sulphur is oxidized by hot nitric acid to sulphur tri- 
oxide, S0 3 . Finely divided carbon or sawdust may be set 
on fire by the strong acid. 

Mtric acid acts upon some organic substances so read- 
ily as to inflame them. A small quantity of oil of turpen- 
tine poured ujjon the strong acid in an open capsule 
ignites with some violence. Hair or silk may be made to 
take fire by holding it in the vapor of boiling nitric acid. 

Nitric acid acts upon all the common metals except 



•NON-METALS. 127 

gold, platinum, and aluminum. It generally forms nitrates, 
but sometimes only oxidizes the metals. Owing to this 
strong oxidizing power hydrogen is never evolved by the 
action of nitric acid upon the metals. The hydrogen dis- 
placed by the metal is oxidized by the remaining acid 
present. It has been shown that if nitric acid is entirely 
free from nitrous acid it acts very slowly, if at all, upon 
many metals. 

In addition to the actions above named, nitric acid acts 
upon a variety of organic compounds, one or more atoms 
of the hydrogen of the organic compound being replaced 
by one or more molecules of N0 2 . The resulting com- 
pounds are very important and will be referred to again. 

Nitric acid is monobasic. 

Uses. Mtric acid is of great importance in the arts; 
among its most important uses may be mentioned the 
manufacture of coal-tar colors, the preparation of nitro- 
compounds, which include nearly all the high explosives, 
of many nitrates used in the arts, and the refining of gold 
and silver. An alloy of copper with gold is readily de- 
tected by touching it with nitric acid, when the copper 
present will give the green nitrate. 

It is remarkable that the dilute acid generally acts 
more readily than the concentrated. This difference is 
now believed to be due to the greater dissociation in solu- 
tion of the weaker acid. 

Nitrates. The nitrates constitute a very important class 
of salts. They are all decomposed by heat and are soluble 
in water (with unimportant exceptions). They are, like 
the acid, oxidizing agents. Powdered lead nitrate and 
charcoal may be exploded by a blow. Common nitre is 
used in gunpowder because of its oxidizing power, and sev- 
eral other nitrates are employed in other explosives. 

The negative chemical properties of nitrogen, its little 
disposition to combine with other elements, and its char- 



128 INORGANIC CHEMISTRY. 

acter as a permanent gas are probably at the basis of the 
instability of its compounds, to which we shall have fre- 
quent occasion to refer. 

The nitrates being generally soluble, they cannot be precipitated, 
and are not so easily detected in solution as the other common mineral 
salts. The easiest test is as follows: Add to the suspected solution in a 
test-tube a solution of iron sulphate; then introduce below the mixed 
liquids concentrated sulphuric acid: if there be present any nitrate, the 
sulphuric acid will liberate the nitric acid, and the ferrous sulphate will 
reduce it to N0 2 , which colors the two liquids at the surface of their 
junction. 

Nitrous Oxide, Laughing Gas, N 2 0. This gas may be ob- 
tained by heating ammonium nitrate in a Florence flask 
fitted with cork and delivery tube. It may be collected by 
displacement over warm water or mercury. The nitrate 
should be heated gently or nitric oxide will be produced. 

Properties. J^ 2 is a colorless transparent gas with a 
slight odor and sweetish taste. It is more soluble than 
oxygen, water dissolving its own volume at 10° C. It sup- 
ports ordinary combustion like oxygen ; the combustion 
is due to the oxygen, the nitrogen monoxide being decom- 
posed and the nitrogen set free. Carbon burned to carbon 
dioxide in nitrogen monoxide produces more heat than 
when burned in oxygen, which shows that heat is evolved 
in the decomposition of nitrous oxide and must have been 
consumed in its production. A substance which absorbs 
heat in its production is called endothermic, one which 
gives it out exothermic. 

Laughing gas is used as an anaesthetic in dental surgery. 
It may be drawn into a test-tube in the liquid state from 
the holder. The liquid supports combustion. It may be 
distinguished from oxygen by its greater solubility and 
sweetish taste. 

Nitric Oxide, NO. This oxide is readily obtained by the action of 
dilute nitric acid upon copper. The metal is oxidized and the acid deoxi- 
dized with the separation of nitric oxide; the metallic oxide formed vt 



NON-METALS. 129 

acted upon by another portion of the acid, copper nitrate being formed. 
The nitric oxide is a colorless transparent gas, but in contact with oxygen 
it unites with it, giving nitrogen tetroxide, if the oxygen be in excess, 
with a very characteristic reddish-brown color. The presence of oxygen 
may be readily detected by the addition of this gas. It will support com- 
bustion if the temperature of the burning body is high enough to decom- 
pose the gas. 

OTHER OXIDES OF NITROGEN. 

Nitrous Anhydride, N 2 3 . There is still some uncertainty as to the 
existence of this compound. The substance generally assumed to be N 2 3 
is very probably a mixture of nitrous and nitric oxides. A solution of the 
substance is believed to contain nitrous acid, though the acid has not been 
isolated. 

Nitrogen Tetroxide. This substance is the main result of the action 
of oxygen upon the nitric oxide. This gas possesses the property of com- 
bining directly with certain metals forming nitro-metals. The tetroxide 
will support combustion if the temperature of the burning body be high 
enough to decompose the gas. 

Nitrogen Pentoxide, N 2 & . The pentoxide may be obtained by dehy- 
drating nitric acid with phosphorus. It is a white crystalline substance. 
It is very unstable, and when suddenly heated explodes with violence. It 
dissolves in water, forming nitric acid. 

CHLORINE; CI. 

Chlorine has not been found in the uncombined state in 
nature. It is a member of an important natural group 
including iodine, bromine, and fluorine. On account of 
the occurrence of the first three in the salts of sea water, 
the group has been called the 7ialogens, and their com- 
pounds the haloid compounds. 

In combination with the metals, chlorine is of abundant 
occurrence, the most common chloride being sodium chlo- 
ride, common salt. In the Stassfurth deposits potassium 
chloride is also an abundant constituent. Many other 
chlorides occur native. 

The chlorides of sodium and potassium, especially the latter, are found 
in animal secretions. Chlorine is also found in combination with hydrogen, 
as hydrochloric acid, in the gases issuing from certain volcanoes. 



130 INORGANIC CUEMISTBT. 

Preparation of Chlorine. Chlorine may be extracted from 
common salt by heating a mixture of the salt and man- 
ganese dioxide with dilute sulphuric acid. The reaction is 
indicated by the equation 

2NaCl + Mn0 2 + 2H 2 S0 4 = Na 2 S0 4 + MnS0 4 + 2H 2 + Cl 2 . 

Chlorine may also be obtained from hydrochloric acid by 
gently heating manganese dioxide alone with it, as indicated 
by the equation 

Mn0 2 + 4HC1 = MnCl 2 + 2H 2 + Cl 2 . 

This gas is a very offensive one to deal with, and special 
precautions and care should be taken in obtaining and ma- 
nipulating it. On the manufacturing scale chlorine has 
until recently been obtained almost entirely by the second 
method. 

It is now prepared in large quantity in Germany by the 
electrolysis of potassium chloride, the other product of the 
operation being potassium hydroxide. In a similar manner 
it is manufactured in England and this country from com- 
mon salt, the other product being sodium hydroxide. 

Physical and Chemical Properties. Chlorine is a greenish- 
yellow gas, with a specific gravity of 35.5 referred to hydro- 
gen. It has a disagreeable suffocating odor and is easily 
liquefied. At ordinary temperature water dissolves about 
two volumes of the gas. For experimentation chlorine is 
collected by displacement or over tepid water; it acts upon 
mercury, and there is considerable loss in collecting it over 
cold water. A strong brine solution dissolves it much less 
readily than water. 

Chlorine has powerful affinities and unites with a great 
number of the other elements even at ordinary temperature. 
Its affinities do not extend to oxygen, but are strongly ex- 
erted towards hydrogen and the metals. Its affinity for 
hydrogen is its most distinguishing characteristic. 



NON-METALS. 131 

It combines directly with hydrogen, bromine, iodine, 
sulphur, arsenic, and phosphorus. Phosphorus finely di- 
vided, or well dried, will take fire in chlorine ; powdered 
arsenic dropj)ed into the gas inflames. 

It combines directly and at ordinary temperature with 
nearly all the metals. Powdered antimony and several 
other metals in the form of thin leaf take fire when dropped 
into the gas. 

On account of its afiinity for hydrogen a lighted wax 
taper plunged into the gas will continue to burn with a 
smoky flame, the hydrogen of the taper burning, the carbon 
being separated. For the same reason many of the hydro- 
carbons will take fire spontaneously ; a strip of bibulous 
paper wetted with oil of turpentine and plunged into the 
gas bursts into flame with a copious liberation of soot; 
a mixture of chlorine and acetylene explodes violently 
when exposed to light. Chlorine is not capable of direct 
combination with carbon, which fact accounts for the sepa- 
ration of the carbon in the cases just cited. 

On account of its attraction for hydrogen it will decom- 
pose water if the solution be exposed to light. A mixture 
of hydrogen and chlorine can be kept in the dark; but if 
exposed to diffused daylight, they combine quietly; if to 
direct sunlight, they combine suddenly with explosion. 

Uses. The most useful applications of chlorine depend 
upon its afiinity for hydrogen. Its most valuable property 
from an industrial point of view is its bleaching power. 
Chlorine added to a solution of indigo or other vegetable 
coloring matter will rapidly discharge the color. The same 
action is observed if cloth dyed with vegetable colors be 
dipped into a solution of chlorine. Colored flowers are 
bleached when dipped into a jar of the gas. 

For bleaching it is essential that water be present, as 
perfectly dry chlorine does not even affect litmus. The 
chemistry of the process seems to be due to the action of 



132 INORGANIC CHEMISTRY. 

the chlorine upon the water, liberating the oxygen, which 
in connection with the chlorine converts the coloring 
matter into oxidized or chlorinized products, which are 
colorless or nearly so. 

Chlorine is largely used in the arts for bleaching linen 
and cotton goods, and rags for the manufacture of paper. 
Silken and woolen goods would be injured by chlorine and 
are bleached with sulphurous acid gas. For bleaching pur- 
poses neither the gas nor its solution is as convenient as 
the combined form, hence it is generally employed in the 
form of bleaching-powder called chloride of lime, from 
which the gas is easily liberated as desired. 

Chlorine is one of the best deodorizers ; by virtue of 
its affinity for hydrogen it breaks up and removes from 
the air hydrogen sulphide and ammonia, both of which 
result from the putrefaction of organic matter and are very 
objectionable. Chlorine is also used as a disinfectant ; its 
affinity for hydrogen and its oxidizing power enable it to 
destroy certain micro-organisms which are injurious to 
health. 

Liquid chlorine is now an article of commerce ; it is put 
up and transported in iron bottles lined with lead; in this 
form it is used in the extraction of gold from its ores. 

HYDROCHLORIC ACID; HC1. 

Occurrence. This acid occurs in nature in the gases emitted 
from volcanoes, and has also been found in the spring 
waters of volcanic districts. 

Preparation. Hydrochloric acid may be produced by the 
direct union of the elements, but for use it is always pre- 
pared by acting upon sodium chloride with sulphuric acid 
as indicated by the following equation : 

NaCl + H 2 S0 4 = NaHS0 4 + HC1. 

The gas may be collected by displacement or over mercury. 



NON-METALS. 133 

By using the proper proportion of the ingredients and a 
higher temperature the reaction for the production of the 
acid can be made to take the form 

2NaCl + H 2 S0 4 = Na 2 S0 4 + 2HC1. 

Hydrochloric acid was formerly obtained in enormous 
quantities as a by-product in the Leblanc process of 
manufacturing sodium carbonate, the first step in the 
operation being indicated by the above reaction. The 
manufacturer of the alkali was compelled to prevent the 
escape of the liberated acid into the air because of its de- 
structive action upon vegetation. Owing to changes in the 
methods of making alkali the hydrochloric acid is now a 
principal product in the Leblanc method. 

The acid vapors resulting from the action of the sul- 
phuric acid upon the salt are thoroughly cooled and then 
brought into contact with a large surface of water by which 
the acid is absorbed 

Properties. Hydrochloric acid is a colorless gas with a 
choking, pungent odor. It fumes strongly in the air by 
condensing the moisture there present. Its formula shows 
it to be heavier than air. It is very soluble in water ; one 
volume of water at' ordinary pressure and 0° C. dissolves 
500 volumes of the gas. As is generally the case, the sol- 
ubility decreases as the temperature rises. The solubility 
of the gas may be illustrated in the same manner as with 
ammonia. 

The common liquid designated as hydrochloric acid is a 
solution of the gas in water ; the strongest solution at 8° C. 
and ordinary pressure contains 43.8 per cent of the acid 
and has a specific gravity of 1.22. The strength of the acid 
may be inferred from its specific gravity. 

If a weak solution of the acid be boiled, it loses water 
and becomes stronger ; if a strong solution be boiled, it 
loses acid and becomes weaker until in each case the solu- 



134 INORGANIC CHEMISTRY. 

tion contains 30 per cent of the acid; this solution distils 
over at a temperature of 110° C. This would seem to in- 
dicate a definite compound between the water and acid in 
the proportion named, but this proportion changes with 
the pressure. 

Commercial hydrochloric acid is usually yellow from 
impurities. It is very likely to contain some chlorine, 
some sulphuric acid, some arsenic, and some iron chloride. 
Mixtures of snow or powdered ice and hydrochloric acid 
make very convenient refrigerants, for certain laboratory 
experiments. 

Hydrochloric acid gas is readily liquefied. The liquid 
acid is colorless, with a specific gravity of .9. It is 
almost without action upon many of the metals which are 
readily attacked by the aqueous solution : it does not even 
act upon lime. Dry hydrochloric acid gas does not act 
upon calcium carbonate. 

Action of Hydrochloric Acid upon the Metals and Metallic 
Oxides. All the metals which decompose water will act 
more readily upon hydrochloric acid, liberating hydrogen 
and forming a chloride. Sodium, potassium, zinc, iron, 
and tin are examples. Hydrochloric acid acts upon alu- 
minum and, when boiling, to a slight extent upon silver. 

The acid acts upon metallic oxides, forming a chloride 
and water, two atoms of chlorine replacing one atom of 
oxygen. Those oxides to which there are no correspond- 
ing chlorides (the less basic oxides) frequently evolve 
chlorine from the acid. Thus while the lower oxide of 
manganese forms manganese chloride (MnCl 2 ), Mn0 2 evolves 
chlorine : 

MnO + 2HC1 = MnCl 2 + H 2 ; 
Mn0 2 + 4HC1 = MnCl 2 + 2H 2 + Cl 2 . 

Of the common metals the dichlorides are soluble in 
water except the dichloride of lead ; the monochlorides 



NON-METALS. 135 

are soluble except those of silver and mercury. Any sol- 
uble chloride in solution gives upon the addition of silver 
nitrate a white curdy precipitate of silver chloride, which 
blackens upon exposure to light and is readily soluble in 
ammonia. This is a very characteristic test for a chloride 
in solution: 

AQUA REGIA ; NITRO- MURIATIC ACID. 

This is a name given to a mixture of three volumes of 
hydrochloric acid and one of nitric acid. The mixture will 
dissolve gold or platinum, while neither of the acids singly 
will do it. A chloride of the metal is formed and the 
power of the mixture depends upon the chlorine liberated: 

HN0 8 + 3HC1 = 2H 2 + NOC1 + Cl 2 . 

COMPOUNDS OF CHLORINE AND OXYGEN. 

Chlorine and oxygen have not been made to combine directly, but there 
are known two oxides of chlorine and four oxy acids; the oxides are C1 2 
and ClOa. The oxides are very unstable bodies and dangerous to handle 
because of their explosive character. 

The oxyacids of chlorine are hypochlorous (HCIO), chlorous (HClOa), 
chloric (HCIO3), and perchloric (HC10 4 ). The salts of the first and third 
are of considerable importance. Some of the metallic hypochlorites are 
useful in bleaching, and potassium chlorate is of practical importance as 
an oxidizing agent; these salts will be referred to under the metal from 
which they are formed. 

COMPOUNDS OF CHLORINE WITH CARBON, SILICON, BORON, 
AND NITROGEN. 

Although chlorine does not combine directly with carbon, several chlo- 
rides of carbon can be obtained by indirect means, as by the action of 
chlorine upon the hydrocarbons, one atom of chlorine removing and com- 
bining with one atom of hydrogen, and another atom of chlorine taking the 
place of the removed atom of hydrogen. This mode of substitution is 
called metalepsis. Chlorine combines directly with silicon and boron. 
With nitrogen it forms a very explosive compound, indicated by the formula 
NCla. This compound is formed by the action of chlorine upon ammonium 
chloride and is very dangerous to handle. 



136 INORGANIC CHEMISTRY, 

BROMINE; Br. 

Occurrence. Bromine is not found free in nature. It 
occurs mainly in combination with potassium, sodium, and 
magnesium in small quantities, in sea water ; more abun- 
dantly in certain mineral waters, as at Kissingen and in the 
mother liquor of the salt works at Stassfurth, Germany, 
and of several of the salt works of the United States. 
Most of the bromine consumed in the United States comes 
from the mother liquor of our salt works, but some from 
Stassfurth. It is obtained in greatest quantity from the 
Ohio brine wells, and some from those of Pennsylvania, 
West Virginia, and Michigan. 

Preparation. After the less soluble salts are separated from the 
mother liquor by evaporation and crystallization, the liquor is introduced 
into a still and acted upon by chlorine. The chlorine liberates the bromine, 
which is carried over by passing steam into the still. The chlorine may be 
produced in the same still or introduced from a separate retort. 

Properties. Bromine is the only non-metallic element 
which is liquid under ordinary conditions ; it has a distinct 
red color ; at 15° C. it has a specific gravity of 3. It emits 
a reddish-orange acrid vapor which is very irritating and 
disagreeable, more so than that of chlorine. Three parts 
dissolve in 100 parts of water by weight. In its chemical 
attributes it resembles chlorine ; it combines directly with 
many metals and non-metals and bleaches like chlorine. 

Little use has been made of bromine, since chlorine can 
generally be used for the same purposes and is much more 
abundant. It has, however, been used as a disinfectant, in 
the manufacture of coal-tar dyes, and in analytical chem- 
istry ; for the last it is much more convenient than chlo- 
rine, being a liquid. For disinfecting, the liquid is ab- 
sorbed by cakes or sticks of kieselguhr or other porous 
earth made plastic by molasses. These sticks absorb a 
large amount of bromine and are kept in tightly stopped 
bottles. 



NON-METALS. 137 

Several bromides are employed in medicine and in pho- 
tography. Bromine is soluble in carbon disulphide and 
ether. 

Hydrobromic Acid; HBr. Bromine combines directly with hydrogen, 
forming hodrobromic acid (HBr), corresponding to hydrochloric acid 
(HC1). 

Oxy acids of Bromine. No oxides of bromine have been obtained, but 
there are two oxyacids similar to the corresponding chlorine acids, hypo- 
bromous acid (HOBr) and bromic acid (HBr0 3 ). 

IODINE; I. 

Iodine has not been found in a free state ; in nature it 
occurs in combination, principally with potassium, sodium, 
magnesium, and calcium as iodides, or together with these 
metals and oxygen as iodates. In combined form it is 
found in sea-water, in many mineral waters, and as sodium 
iodate (NaI0 3 ) in the Chilian nitre beds. 

Preparation. The two principal sources of iodine are 
kelp (the ashes of seaweed) and the native Chilian salt- 
petre or "caliche." The latter source now furnishes the 
greater proportion of iodine. 

Many varieties of seaweed extract the iodine from sea-water as a neces- 
sary portion of their food; when these weeds are burned the iodine is left 
in the ashes or "kelp," together with a large number of other salts. The 
iodine is mainly in the form of iodides of sodium and potassium. These 
iodides are separated from the other salts as perfectly as possible, and then 
the iodine is liberated by the combined action of sulphuric acid and man- 
ganese dioxide, exactly as chlorine is liberated from common salt. 

In the " caliche " the iodine is in the form of sodium iodate (NaI0 8 ), 
from which it is precipitated by the action of acid sodium sulphite. 

Properties. Iodine is a crystalline solid of a bluish-black 
color, resembling graphite. In the solid state its specific 
gravity is nearly 5. It volatilizes sensibly at ordinary tem- 
perature, diffusing an odor resembling that of chlorine. It 
fuses at 114° C. and gives a beautiful violet vapor which is 
one of the heaviest known gases, being nearly nine time? 



138 INORGANIC CHEMISTRY. 

as heavy as air. At a higher temperature the color of the 
vapor changes and its density becomes less. 

It is slightly soluble in water, readily soluble in carbon 
disulphide, benzene, petroleum spirit, and solution of 
potassium iodide and alcohol. 

In chemical properties it resembles chlorine and bro- 
mine, but is less energetic, being displaced from its com- 
pounds by these elements. It combines directly with 
many elements both metallic and non-metallic. Phosphorus 
placed in contact with powdered iodine at once takes fire, 
as also does powdered antimony when dropped into iodine 
vapor. In the presence of water it attacks gold. When 
brought into contact with starch it gives a sky-blue color ; 
this is a very delicate test for free iodine and will reveal 
the presence of a millionth part in solution ; iodine in com- 
bination will not affect the starch. 

Uses. Iodine is largely used in the manufacture of 
aniline colors, but the bulk of its compounds is used in 
medicine. A small quantity is also used in photography, 
the iodides of silver, potassium, ammonium, and cadmium 
being used for this purpose. 

The tincture of iodine is a mixture of iodine and potas- 
sium iodide dissolved in alcohol. Iodine dissolved in car- 
bon disulphide gives a solution opaque to light but trans- 
parent to heat. To give the starch test the iodine must be 
in the free state, and, as it nearly always exists in combina- 
tion, it is necessary to add to the liquid under examination 
some agent to liberate the iodine. The test is usually 
made by adding to the suspected liquid a little starch 
paste, then a little chlorine water ; the chlorine will lib- 
erate the iodine if present in the form of an iodide. 
Iodine is of course an equally delicate test for starch. 

Iodine can be combined directly with hydrogen to form hydrogen iodide 
or hydriodic acid; this acid is very similar to hydrochloric and hydro- 
bromic acids. 



NON-METALS. 139 

Iodine can be directly oxidized by ozone, but the composition of the 
resulting compound is not certainly known. The only definitely known 
oxide is I 2 5 ; this oxide is the anhydride of iodic acid (H 2 0,I 2 5 = 2HI0 3 ). 
Iodic acid (HI0 3 ) has been isolated, but there are salts corresponding to 
several periodic acids, some of which have not been isolated. 

Other Compounds of Iodine. Iodine combines with carbon, nitrogen, 
and boron, forming compounds similar to the chlorine compounds of the 
same elements. 

Considering the chemical resemblance of chlorine, bromine, and iodine, 
it is very remarkable that the elements all combine with each other. 

FLUORINE ; F. 

Occurrence. Fluorine occurs in combined form as fluor-spar (CaF 2 ), 
sometimes called Derbyshire spar on account of its abundant occurrence in 
Derbyshire. It is also present in the mineral cryolite, a double fluoride of 
aluminum and sodium. In small quantity it is present in a number of 
other minerals, in the bones, and in the enamel of teeth. Fluor-spar is 
the most abundant compound containing it. This mineral crystallizes in 
cubes or octahedrons with varying shades of color, some of which are very 
delicate and beautiful. 

Preparation and Properties. Fluorine was not isolated until 1886. 
It was then obtained by decomposing hydrofluoric acid (HF) by electricity. 
It is a colorless gas and the most chemically active element known. On 
account of its intense disposition to combine with other elements, it re- 
sisted until recently all attempts to isolate it. It decomposes water in- 
stantly, and combines readily with mercury. It explodes with hydrogen 
even in the dark, and combines with combustion with many non-metals, 
attacks the metals, and even attacks glass. No compound with oxygen is 
known. 

Hydrogen Fluoride; HF. This is the most important compound of 
fluorine. The pure acid can be obtained by heating acid potassium fluoride 
in a platinum retort, with platinum tube and condensing arrangement 
cooled by a freezing mixture. The acid thus obtained is a colorless liquid 
a little lighter than water. It has a strong affinity for water and produces 
a hissing noise when brought into contact with it. A solution of hydro- 
fluoric acid in water is obtained by heating powdered calcium fluoride 
(CaF 2 ) with sulphuric acid: 

CaF a + H.SO, = CaSO< + 2HF. 

This operation is performed in a leaden retort with tube and condenser o\ 
the same metal, the condenser being cooled by a freezing mixture. The 



140 INORGANIC CHEMISTRY. 

solution possesses powerfully acid properties, and the vapor escapes rapidly 
from the water as the temperature rises. 

The dilute acid dissolves all ordinary metals except platinum, gold, 
silver, mercury, and lead. It also readily attacks glass if the least moisture 
be present, though it has been found that the anhydrous acid does not 
affect glass. 

Uses. The principal use of hydrofluoric acid depends upon its power 
of acting upon silica and silicates. Powdered sand may be dissolved in 
the aqueous solution of the acid, and if the solution be evaporated the 
silica will volatilize as silicon fluoride (SiF 4 ). If a silicate be digested and 
heated with the acid, a fluoride of the base will be left. 

The action of the acid upon glass is explained by its power of attacking 
silica, for glass is a mixture of two or more silicates. 

A design maybe etched or engraved upon glass as follows: Let the plate 
be coated with wax or etching-ground and the design drawn with a pointed 
instrument, cutting through the wax. The plate is then placed with the 
waxed side down over a shallow leaden dish, which contains calcium 
fluoride and sulphuric acid. Upon the application of a little heat the acid 
is disengaged and speedily makes the impression upon the glass. If the 
engraving is done with the vapor of the acid, the design is dull or opaque; 
if the liquid acid is employed, the lines are transparent. 

The gaseous acid does not produce an uniform opacity and is therefore 
not generally suitable for the purpose. For opaque etchings a solution of 
the acid fluorides of the alkalies is used, usually one containing some potas- 
sium or ammonium sulphate. 

SULPHUR; S. 

Occurrence. Sulphur is an elementary body of great impor- 
tance. It occurs abundantly in the free state, and also as a 
constituent in many combined forms. In the uncombined 
form it is usually though not invariably found in volcanic 
regions. In some localities it is being deposited from 
chemical actions now taking place. These are called ' ' liv- 
ing sulphur beds " and occur in the regions of geysers, hot 
springs, fumaroles, and other evidence of recent volcanic 
activity. 

The free sulphur is also found disseminated through 
stratified deposits, alternating with beds of clay or other 
minerals. 






NON-METALS. 141 

Sicily produces the greatest amount of native sulphur. 
In the U. S. it is obtained in great quantity from the 
Louisiana mines. The mines of Nevada and Utah supply 
a small amount of sulphur. It occurs in many other 
places throughout the world. 

In the combined form it occurs in the sulphides of many 
metals, the most important being iron pyrites, FeS 2 ; copj)er 
pyrites, CuFeS 2 ; galena, PbS; zinc blende, ZnS; and cinna- 
bar, HgS. It occurs in hydrogen sulphide in many mineral 
waters ; also in many natural sulphates, the most important 
being those of calcium, lead, strontium, magnesium, and 
sodium. 

Extraction of Crude Sulphur from the Native Ore. Liquation 
Process. All native sulphur must be separated from the 
mineral impurities which accompany it. This is usually 
done by the liquation process, or melting out the sulphur; 
there are several ways of accomplishing this. The sulphur 
ore is sometimes made into a kiln, and the sulphur is melted 
out by smothered combustion, a portion of the sulphur 
itself being consumed to furnish the heat. This method, 
though wasteful as regards sulphur, is cheap in other re- 
spects, and is employed to a large extent. The heat for 
driving out the sulphur may be obtained from extraneous 
fuel. High-pressure steam has also been employed for 
melting sulphur out of its ores; in this case the ores are 
subjected to the action of the steam in closed iron vessels. 
A solution of calcium chloride in water with boiling-point 
at 120° C. is sometimes used to furnish the heat for melting 
out the sulphur. 

The ores of sulphur are sometimes enclosed in retorts 
and subjected to distillation, the sulphur being condensed 
in the liquid state. 

Purification of the Crude Sulphur. Sulphur obtained 
by any of the above processes usually contains a few per 
cent of earthy impurities, from which it is freed by dis- 



142 INORGANIC CHEMISTRY. 

tillation. If the vapor of the sulphur is condensed in a cham- 
ber below the melting-point, it gives a pale yellow powder 
known as sublimed sulpliur on flowers of sulphur. When 
the temperature of the chamber rises sufficiently high the 
flowers melt and are run out into sticks, giving the roll 
sulphur or brimstone. 

The Louisiana product issues from the wells in liquid 
state and is of such purity that it goes into the market 
without further treatment. 

Extraction of Sulpliur from the Sulphides. Sulphur was 
formerly obtained in considerable quantity from iron sul- 
phide (FeS 2 ) by heating it in the absence of air. At a very 
high temperature nearly one half the sulphur can be sepa- 
rated, but at ordinary furnace heat only about one fourth is 
separated. This method of preparing sulphur has practi- 
cally ceased as a manufacturing industry, the pyrites being 
used for making sulphuric acid. 

Sulphur can also be obtained from copper pyrites by 
roasting with proper precautions. This is sometimes done 
in the process of roasting the ore preliminary to the ex- 
traction of the copper. 

The sulphur from the pyrites is generally found to con- 
tain impurities associated with those minerals, and is puri- 
fied by subsequent treatment. 

Sulphur from Other Sources. Sulphur is obtained in some quantity 
from the waste products of the gas-works, and in still greater amount from 
the waste products of the alkali-works. Its presence in these products will 
be explained subsequently. 

Physical Properties of Sulphur. As ordinarily seen sul- 
phur is a lemon-yellow, brittle, crystalline solid, insoluble 
in water but soluble in carbon disulphide. It exhibits 
several allotropic modifications, the two most characteristic 
of which are marked by their action with the same solvent, 
one form being soluble in carbon disulphide, the other 
form not. 



NON-METALS. 143 

The soluble varieties of sulphur show two distinct crystalline forms: 
one, the native form of sulphur, is the rhombic octahedron, the same form 
which results when it crystallizes from solution; the other is the oblique 
prismatic which results when it cools after melting. The distinction be- 
tween these crystalline forms extends to their fusing-points and their 
specific gravities, the first having the higher specific gravity but lower 
fusing-point. 

The insoluble form of sulphur shows several uncrystalline varieties, the 
most important of which are the ductile and the amorphous. The ductile 
sulphur results when boiling sulphur is poured in a thin stream into water; 
it is soft and elastic like rubber. The amorphous sulphur is always formed 
when the flowers of sulphur are deposited, and will be left undissolved if 
the flowers be treated with carbon disulphide. Milk of sulphur is a soluble 
amorphous form of sulphur obtained as a precipitate by the addition of an 
acid to an alkaline solution of sulphur. This form is white and milky in 
appearance and is a medicinal preparation. If a solution of sulphur di- 
oxide be decomposed by electricity sulphur appears at the negative pole 
as an insoluble amorphous variety, while if a solution of hydrogen sul- 
phide be electrolyzed the sulphur appears at the positive pole as a soluble 
amorphous variety. For this reason the soluble varieties have been 
classed as electro-negative, and, the insoluble as electro-positive. 

Chemical Properties. Sulphur possesses energetic affini- 
ties, combining directly with a large number of elements. 
Many of the sulphides in atomic constitution correspond 
with the oxides of the same elements. Any modification 
of sulphur heated in the air or oxygen takes fire and burns 
with a pale blue flame, producing sulphur dioxide. Finely 
divided sulphur, especially flowers of sulphur, is slowly 
oxidized in moist air, yielding sulphuric acid. 

Sulphur in a finely divided state will combine with 
some of the metals at ordinary temperature, and at a high 
temperature it will combine with nearly all the metals and 
with all the non-metals except nitrogen. It can very read- 
ily be made to display electrical properties, as may be 
shown by friction or by powdering in a dry mortar. 



144 INORGANIC CHEMISTRY. 

COMPOUNDS OF SULPHUR AND HYDROGEN. 

There are at least two compounds of hydrogen and sulphur. The most 
important, hydrogen sulphide, is analogous in composition to water, having 
the formula H 2 S. The other, hydrogen persulphide, contains a larger pro- 
portion of sulphur. Its formula has not been definitely determined, but is 
thought to be H 2 S 2 , though it may contain a larger proportion of sulphur. 
There are reasons for thinking that still more complex compounds exist. 

HYDROGEN SULPHIDE ; H 2 S. 

Occurrence. This gas is present in the waters of many 
springs, which has caused them to be called sulphur- 
springs, and such mineral water sulphur-water. It is found 
in large quantity among the gases issuing from volcanoes. 
It is very generally present among the products which re- 
sult from the putrefaction of organic matter containing 
sulphur, both animal and vegetable. The offensive odor of 
rotten eggs is mainly due to it, and it generally contributes 
to the unpleasant odors from sewers and drains. The gas 
is also found among the products of the destructive distil- 
lation of coal and other organic substances containing 
sulphur. 

Properties of Hydrogen Sulphide. It is a colorless gas 
with the odor of putrid eggs and faintly sweetish taste. 
It is liquefied by . a pressure of seventeen atmospheres. 
Water at ordinary temperature dissolves about three times 
its volume. The aqueous solution is acid to test-paper and 
has the 'taste and smell of the gas. The gas is readily com- 
bustible, giving the blue flame of sulphur. When the sup- 
ply of oxygen is abundant the products of the combustion 
are water vapor and sulphur dioxide, 

H 2 S + 3 = H 2 + S0 2 , 

and when mixed with oxygen in the proportions indicated, 
and ignited, the mixture explodes. If the supply of oxygen 
be limited some of the sulphur will be deposited. 

In the presence of moisture and oxygen the gas is de- 



NON-METALS. 145 

composed with tlie deposition of sulphur ; hence the solu- 
tion of the gas in water cannot be kept for a great while : 
light produces the decomposition. The gas acts as a poison 
if inhaled in large quantities, and even when much diluted 
with air it gives rise to disagreeable symptoms. 

Hydrogen sulphide is decomposed into its elements at 
a temperature a little above 400° C. Chlorine and bromine 
decompose it at ordinary temperature, removing the hydro- 
gen and depositing the sulphur. On account of its ready 
decomposability hydrogen sulphide acts as a reducing 
agent ; thus when heated with concentrated nitric or sul- 
phuric acid the hydrogen is oxidized and the sulphur de- 
posited. 

Action with the Metals and Metallic Oxides. Many of the 
metals and metallic oxides act upon sulphuretted hydrogen 
in a manner resembling the action of the other hydrogen 
acids. With some of the metals, as mercury, silver, and 
lead, this action takes place at ordinary temperature. 
When heated in the gas several other metals decompose it. 
It is because of its action upon silver that silver plate and 
other articles of silver often tarnish ; silver egg-spoons are 
blackened by the sulphur present in eggs. 

Hydrogen sulphide acts upon many metallic oxides, 
forming metallic sulphides and water, according to the gen- 
eral formula 

MO + H 2 S = MS + H 2 0. 

Action of Hydrogen Sulphide with Metallic Salts. Hydrogen 
sulphide is one of the most valuable reagents in the chem- 
ical laboratory because of its disposition to act upon solu- 
tions of metallic salts. When hydrogen sulphide is brought 
into contact with solutions of metallic salts, characteristic 
precipitates are often formed. These precipitates are in- 
soluble sulphides produced by the double decomposition 
of the dissolved salt and the hydrogen sulphide, some acid 
being produced at the same time due to the combination 



146 INORGANIC CHEMISTRY. 

of the acid radical of the salt with the hydrogen liberated 
from the hydrogen snlphide. This action may be repre- 
sented by the general equation 

2MR + H 2 S = 2HR + M 2 S. 

All metals are thus precipitated from their solutions 
provided their sulphides are insoluble in the products of 
the reactions, water and dilute acid. Those metallic sul- 
phides which are soluble in or decomposed by dilute acid 
would of course not be precipitated by the reaction above 
indicated. Many metals whose sulphides are soluble in 
acid solutions may be precipitated from the solutions of 
their salts by the use of an alkaline sulphide instead of 
hydrogen sulphide. The alkaline sulphide generally used 
for the purpose is ammonium sulphide, (NH 4 ) 2 S, and the 
action is indicated thus : 

2MR + (NH 4 ) 2 S = M 2 S + 2NHJR. 

From this reaction it will be seen that no acid is liberated, 
and if the metallic sulphide represented in the second 
member is insoluble in the products of the reaction, it will 
be precipitated. 

The metals may accordingly be divided into three classes : 1. Those 
whose sulphides are soluble in water; 2. Those whose sulphides are insolu- 
ble in water and dilute acid; 3. Those whose sulphides are soluble in dilute 
acids, but insoluble in water and dilute alkaline solutions. The first class 
is not affected by hydrogen sulphide; the members of the second class are 
precipitated from a solution of their salts by hydrogen sulphide, and those 
of the third by the addition of ammonium sulphide. 

The sulphides of the different metals often have very 
characteristic colors, which taken, in connection with reac- 
tions when treated with certain reagents, give the means of 
distinguishing and thus determining the metal present in 
a given solution. 

The action of hydrogen sulphide with the oxides and 
Baits of lead explains the discoloration of lead paint which 



NON-METALS. 147 

so frequently occurs. Any paint in which lead is an ingre- 
dient is liable to discoloration by hydrogen sulphide, due 
to the formation of lead sulphide. Paintings so discol- 
ored are sometimes partially restored by continued ex- 
posure to light and air, the lead sulphide being converted 
into lead sulphate. The presence of hydrogen sulphide in 
gas may be detected by moistening a paper with a solution 
of lead nitrate or lead acetate and exposing it to the action 
of the gas. The paper is blackened if a trace of hydrogen 
sulphide be present ; if the gas be in solution it will imme- 
diately blacken upon the addition of a soluble salt of lead. 
In each case the dark color is due to the formation of lead 
sulphide. The converse of course holds, and the presence 
of lead in solution may be detected by the addition of hy- 
drogen sulphide or any soluble sulphide. 

Preparation of Hydrogen Sulphide. It may be prepared by 
the direct union of its elements, but for laboratory pur- 
poses it is generally obtained by the action of sulphuric or 
hydrochloric acid upon iron monosulphide : 

2HC1 + FeS = FeCl 2 + H 2 S ; H 2 S0 4 + FeS == FeS0 4 + H 2 S. 

The gas is given off without the application of heat. 
Obtained in this way the hydrogen sulphide nearly always 
contains hydrogen due to the presence of free iron in the 
iron sulphide. 

The pure gas may be prepared by heating antimony 
sulphide with hydrochloric acid : 

Sb 2 S 3 + 6HC1 = 2SbCl 3 + 3H 2 S. 

In this method hydrochloric acid must be used, for dilute 
sulphuric acid scarcely acts upon the antimony sulphide, 
and the concentrated decomposes the hydrogen sulphide 
liberated. 

The natural salts of hydrogen sulphide constitute an 
important class of ores of the useful metals ; their proper- 
ties will be subsequently described. 



148 INORGANIC CHEMISTRY 

COMPOUNDS OF SULPHUR AND OXYGEN. 

Four oxides of sulphur are known : the dioxide, S0 2 ; the trioxide, SO*; 
the sesquioxide, S 2 3 ; and the persulphuric oxide, S 2 7 . The first two 
are important; the last two are scarcely known in the separate state and 
will not be described. 

SULPHUR DIOXIDE ; S0 2 . 

Occurrence. Sulphur dioxide occurs in the gaseous 
emanations from volcanoes and has been detected in the 
waters of certain volcanic springs. It is sometimes present 
in the air of towns or in the neighborhood of manufactur- 
ing works, in these cases resulting from the combustion of 
the sulphur of the fuel or by liberation in some chemical 
process. It has already been stated that sulphur dioxide 
is always the product of the combustion of sulphur in air 
or oxygen. It is removed from the air by oxidation being 
eventually converted into sulphuric acid. 

Physical and Chemical Properties of Sulphur Dioxide. This 
gas is liquefied at ordinary temperature under two atmos- 
pheres of pressure. Its boiling-point is — 8° C, and it 
produces great cold by its evaporation. Water dissolves 
about 40 times its volume at ordinary temperature, and 
the solution is believed to contain sulphurous acid, but the 
acid has not been obtained in the separate state. Its formula 
shows it to be over twice as heavy as air. It extinguishes 
flame and is sometimes used to extinguish burning soot in 
a chimney, the sulphur being burned in the fireplace. It 
is a stable compound and not readily decomposed ; at a 
high temperature it will combine with oxygen, passing to 
sulphur trioxide. It is poisonous, causing death very 
quickly when breathed in a pure state, and being injurious 
in even small quantity. 

Preparation. In the laboratory sulphur dioxide is gen- 
erally prepared by deoxidizing sulphuric acid by heating 
with copper or carbon : 



NON-METALS. 149 

2H 2 S0 4 + Cu = C11SO4 +■ 2H 2 + S0 2 ; 
2H 2 S0 4 + C = C0 2 + 2H 2 + 2S0 2 . 

The first is the more convenient method for all ordinary 
illustration. 

As a general rule it may be stated that those metals 
which act upon sulphuric acid at common temperature 
liberate hydrogen, while those which act only at elevated 
temperature liberate sulphur dioxide. Owing to its great 
specific gravity the gas may be collected by displacement 
or over mercury. 

Uses. Sulphur dioxide is extensively used as a bleach- 
ing agent for wool and straw goods, which would be injured 
by chlorine. The presence of water is necessary for the 
action; consequently the goods are usually moistened and 
subjected to the action of the gas. In bleaching the sul- 
phurous acid often appears not to destroy the coloring 
matter, but to form colorless compounds with it, for the 
original color frequently returns after the lapse of time. In 
other cases the action appears to be due to the abstraction 
of oxygen from the dye, leaving it colorless. 

The solution of the gas in water, forming sulphurous 
acid, is found to possess great deoxidizing power, which is 
thought to be due to reactions by which hydrogen is liber- 
ated, the liberated hydrogen then abstracting the oxygen 
from the other body. 

Sulphur dioxide still further resembles chlorine in that 
it is used as a disinfectant. Clothes and buildings are often 
fumigated by burning sulphur, but its action in this respect 
has been over-estimated. It has also been used as an anti- 
septic or preservative, as it prevents and stops fermenta- 
tion. Wine and beer casks are sometimes treated with it 
to prevent change in the fresh liquor introduced. Cer- 
tain salts of sulphurous acid maybe used for the same 
purpose. 



150 INORGANIC CHEMISTRY. 

Sulphurous Acid and Sulphites. The solution of sulphur dioxide in 
water is believed to contain sulphurous acid, H 2 S0 3 . This compound is 
not known in a free state, but a large number of salts is known which can 
be obtained by treating the gaseous solution in water with bases. This 
fact justifies the conclusion that the acid exists, and its salts indicate the 
formula H 2 S0 3 . The acid characters of the compound are not strong and 
it is very unstable, soon passing to sulphuric acid. The salts are of course 
called sulphites, and as the acid is bibasic there are two kinds. Sodium 
sulphite is largely used in the manufacture of paper to destroy the excess 
of chlorine used in the bleaching. 

Sulphur Trioxide, Sulphuric Oxide, Sulphuric Anhydride, S0 3 . This 
compound may be formed by the direct union of sulphur dioxide and oxy- 
gen, by passing a mixture of the gases through a tube containing finely 
divided platinum. It may also be obtained by gently heating fuming sul- 
phuric acid as indicated by the equation 

H 2 S 2 7 (heated) = H 3 S0 4 + S0 3 . 

Pure sulphur trioxide is a liquid at ordinary temperature. It crystal- 
lizes when cooled in long transparent prisms which melt at 14.8° G. It 
fumes in the air, and the solid form soon deliquesces. The oxide combines 
violently with water, forming sulphuric acid. A piece of the solid oxide 
dropped into water hisses similarly to a red-hot iron. It is decomposed by 
heat into sulphur dioxide and oxygen. 



SULPHURIC ACID; H 2 S0 4 . 

Sulphuric acid is of fundamental importance both in the 
arts and sciences, and, in fact, is the most important and 
useful acid known. It is a principal agent in the prepara- 
tion of inorganic acids already described, and of nearly all 
other acids. In a great majority of the arts and trades 
sulphuric acid finds a greater or less application. The 
variety and extent of the demand for this acid makes its 
manufacture one of the most extensive and important of 
modern industries. Owing to the above facts, theory and 
practice combine to perfect the process of its manufacture, 
which has now reached a high state of perfection. 



NON-METALS. 151 

The other important inorganic acids are obtained from 
their salts, but this one is mainly made from its elements, 
built up from its constituents. The constituent raw mate- 
rials most abundantly required in the manufacture are 
sulphur, oxygen, and water vapor, the last two being 
essentially without cost. 

The Leaden Chamber Process. The principal process em- 
ployed depends upon the fact that sulphur dioxide, in the 
presence of water vapor and certain oxides of nitrogen and 
the oxygen of the air, is converted into sulphuric acid. 
The fundamental reaction-results may be expressed as 
follows : 

3S0 2 + 2HN0 3 + 2H 2 = 3H 2 S0 4 + 2NO ; 
2NO + 2 = 2N0 2 ; 2N0 2 + 2S0 2 + 2H 2 = 2H 2 S0 4 + 2NO. 

The last two operations are continually repeated. 

It appears that the nitric oxide acts as a carrier of 
oxygen, taking it from the air and becoming nitric per- 
oxide. By transfer of oxygen to the sulphurous oxide the 
peroxide is reduced to nitric oxide ; this operation is 
repeated continuously. If no loss of the nitrogen oxides 
occurred, a given quantity of nitric oxide would suffice to 
convert an indefinite amount of sulphurous oxide into 
sulphuric acid, but owing to unavoidable loss it is neces- 
sary to constantly replenish this compound. This is 
usually done by generating a small quantity of nitric acid 
by the action of sulphuric acid upon sodium nitrate, and 
the nitric oxide is produced as indicated in the first of the 
above equations. 

The process of manufacture is as follows : Sulphur or 
metallic sulphides are burned in the air to produce sulphur 
dioxide. A small amount of the vapor of nitric acid is 
produced by the action of sulphuric acid upon sodium 
nitrate, which vapor is caused to mingle with the sulphur 
dioxide and the oxygen of the air. To this mixture of 



152 



INORGANIC CHEMISTRY. 



gases in suitable apartments is added the proper amount 
of steam, when the reactions above indicated take place. 

The plant employed in the process, shown in section at Fig. 9, consists 
of : 1st. The burner, in which the sulphur or sulphides are burned for the 




Fig. 9. 

production of the sulphur dioxide. Through these burners is also admitted 
the air to supply the oxygen required for the formation of the vitriol. 
2d. The arrangements employed for the production and introduction of 
the nitric acid vapor. These differ, but that most generally used con- 
sists of a series of earthenware or iron pots which are placed in the 
u nitre oven" ; these pots receive the charge of sulphuric acid and nitre 
for the production of nitric acid. The " nitre oven " is usually a receptacle 
placed in some part of the burner or its flues, so that the heat from the 
burner promotes the evolution of the nitric acid, and the vapor of the acid 
is carried along with the air and sulphur dioxide through the flue Q into 
the tower E. 3d. The chambers, which are immense rooms completely lined 
with sheet lead. They vary in number and size; usually, however, there 
are three or four with a capacity of from 40,000 to 80,000 cubic feet each. 
Into these chambers the gases from the burners are introduced, and at 
various points jets of steam are projected into them. The floors of 
the chambers are soon covered with a solution of sulphuric acid. 4th. In 
addition to the above-mentioned parts of the plant there are supplementary 
appliances generally used, the most important of which are two towers, 
one situated between the burners and the chambers, and the other at the 



NON-METALS. 153 

exit end of the last chamber. The tower at the exit end of the chambers 
is to prevent the waste of the oxides of nitrogen while the nitrogen of the 
air, which takes no part in the chemical action in the chambers, is being 
removed therefrom. This exit, called Gay-Lussac's tower, is a tall chamber 
filled with porous material over which oil of vitriol is allowed to flow. The 
useless nitrogen escapes from the tower by a flue leading from the top of 
the tower to the chimney-stack of the works, while the oxides of nitrogen 
are absorbed by the oil of vitriol. The acid from this tower is pumped up and 
caused to descend over acid-proof brick in another tower (Glover's), which 
is placed between the burners and the chambers. The hot gases from the 
burners also pass through Glover's tower E, and in so doing they take up 
the oxides of nitrogen from the " nitrous " vitriol and return them to the 
chamber. The hot gases from the burners in passing through Glover's 
tower also carry back steam into the chambers and thus save fuel in steam- 
raising. In the Glover tower the production of sulphuric acid takes place 
to a greater extent than in any other part of the chambers of the same 
cubical contents. The towers are not in universal use, but they accom- 
plish great economy in the manufacture. When a Glover tower is used 
the whole of the chamber acid, as well as that from the Gay-Lussac tower, 
may be passed through it; the chamber acid is thus concentrated by the 
heat of the gases from the burners, and the gases are themselves cooled to 
the required temperature. 

After the chamber acid is passed through the Glover tower it has a 
specific gravity of about 1.72, and is strong enough for many rough chemical 
manufactures. If the chamber acid is not sent through the Glover tower, 
it is taken from the chambers when it reaches the specific gravity of about 
1.60, for it then begins to absorb the oxides of nitrogen. This acid is 
strong enough for some applications, but is usually further strengthened 
by heating in leaden pans until it reaches a specific gravity of about 1.72. 

The concentration cannot be carried further in leaden pans because of 
the action of the acid upon the lead. 

The acid of specific gravity of 1.72 contains about 80 parts of sulphuric 
acid, and for greater strength the evaporation is carried on in glass, plati- 
num, or iron stills, and this is the most expensive part of the operation 
The concentrated acid of commerce thus obtained contains 98 parts of sul- 
phuric acid and has a specific gravity of 1.84. The commercial acid gen- 
erally contains some impurities, the most common of which are iron 
sulphate, lead sulphate, oxides of nitrogen, and arsenic. The last two may 
be removed by proper treatment, and the first two by the actual distillation 
of the acid. 



154 INORGANIC CHEMISTRY. 

At a distance from the factories the cost of the acid is largely increased 
because of the risk involved in the transportation. In case of breakage or 
leakage in transportation it is a very difficult body to manage. 

Pyrites now supplies the sulphur for much the larger 
proportion of sulphuric acid. In America the greater por- 
tion of the sulphur is from native sulphur, but the pyrites 
industry is constantly growing. The United States now 
produces annually a million tons of sulphuric acid. The 
greatest uses of the acid in this country are in the phos- 
phate industries and in the refining of petroleum and 
manufacture of high explosives.* 

Physical and Chemical Properties of the Acid. The concen- 
trated acid obtained by the processes described always 
contains from one to two per cent of water. By evapora- 
tion all the weaker acids finally attain this composition and 
then distil over unchanged at the temperature of 338° C. 
The vapor evolved during the distillation is not that of 
sulphuric acid, but is a mixture of sulphur trioxide and 
water vapor which pass over and condense together in the 
receiver. If pure, the acid is a colorless, heavy, oily 
liquid. 

The acid has a powerful affinity for water and readily 

* Mr. W. R. Quinan, late superintendent of the California Powder Works 
informed the writer that advantageous improvements have recently been 
introduced in this country in acid manufacture. When pyrites is used as a 
source of sulphur it is almost impossible to obtain a perfectly clear acid, but 
by the improvements just referred to certain works have succeeded in produc- 
ing a commercial acid of 96 per cent strength in the Glover tower. This is done 
by lining the tower with very refractory material and greatly raising the tem- 
perature of the tower by conserving the heat from the burners. From the 
same authority it is learned that certain of the American works have succeeded 
in producing an artificial draft through the chambers by means of rotating fans 
placed in the flue at the end of the chamber system. This plan was first tried 
in Germany, but did not succeed then. This permits the production of a much 
greater amount of acid in the same chamber space. The acid chambers at* 
tached to the works above referred to yield three pounds of concentrated H-S0 4 
to each pound of sulphur burned. 



NON-METALS. 155 

absorbs moisture from the atmosphere ; for this reason it 
is often nsed as a desiccating agent. It is thus employed 
in the laboratory for drying without heat. The objects to 
be dried are placed over a dish of sulphuric acid in a closed 
vessel, and the operation is greatly facilitated by exhaust- 
ing the air from the vessel. The acid is also frequently 
used to dry gases, the gases being made to pass over a sur- 
face of the acid. Pumice-stone soaked in the acid is ad- 
mirably adapted for exposing the gases to the action. 

The acid combines energetically with water, so that 
caution is always necessary in mixing them ; the acid 
should always be poured into the water, and not the re- 
verse. The temperature produced by mixing the acid and 
water often exceeds that of boiling water. If four parts of 
the acid be added to one of powdered ice or snow there is 
an elevation of temperature, but if the proportions be re- 
versed there is a reduction of temperature. 

Owing to its affinity for water the acid decomposes many 
organic compounds containing hydrogen and oxygen, re- 
moving from the bodies these elements in the proportions 
to form water ; it thus acts upon alcohol and oxalic acid. 
In a similar manner it acts upon paper, wood, and sugar, 
removing the oxygen and the hydrogen in the proportion 
to form water and leaving the carbon in excess, with the 
result of charring the body. This action is finely illustrated 
in the case of sugar as follows : Dissolve some crystalline 
cane sugar in three fourths its weight of warm water and 
allow it to partially cool ; then add a volume of concen- 
trated acid equal to two thirds of the volume of the water 
used : the liquid blackens and froths up as a spongy mass 
of carbon. Even when much diluted the acid corrodes and 
destroys textile fabrics. 

Under the influence of heat it decomposes the salts of 
all acids more volatile than itself. On this account the 
acid is often said to be the strongest of the mineral acids, 



156 INORGAXIC CHEMISTRY. 

but this ability to decompose the salts of other acids is not 
alone the test of the strength of an acid, as has already 
been pointed out. 

At a red heat the vapor of the acid is decomposed ac- 
cording to the following equation : 

H 2 S0 4 (heated) = S0 2 + H 2 + O. 

Acids corresponding to the formula H 2 S0 4 , of 100 per cent purity, can 
be obtained by adding to the concentrated acid the exact amount of sul- 
phur trioxide to combine with the water there present. "When the con- 
centrated acid containing 97 or 98 per cent of sulphuric acid is cooled to 
— 10° C. or below that point, the pure acid crystallizes and may be sepa- 
rated in the pure state ; the latter process is now carried on upon a manu- 
facturing scale. 

In combining with water the acid forms several definite compounds, the 
best known of which are the combinations resulting from the union of one 
molecule of acid with one or two molecules of water, which may be respec- 
tively represented by the formulas H 2 S0 4 ,H 2 and H 2 S0 4 ,2H a O. 

SULPHATES. 

Sulphuric acid acts readily upon metallic oxides and 
carbonates, converting them into sulphates, in the latter 
case, with the evolution of carbon dioxide. Sulphuric acid 
cold or hot dissolves all the metals except gold and plati- 
num. The boiling acid attacks silver, forming the sul- 
phate with evolution of sulphur dioxide. Under the same 
conditions it also acts slightly upon platinum. The very 
strong acid does not act upon cast iron, This metal can 
therefore be used for concentrating the acid after it reaches 
the strength which attacks platinum. Before it reaches 
this strength it acts more readily upon iron than platinum. 
In the California powder works the last concentration takes 
place in iron retort, and Mr. Quinan states that chilled cast 
iron offers a high degree of resistance even to weaker acid. 
Gold is not acted upon, hence the acid is often used in 
separating gold and silver or parting these metals. Gren- 



NON-METALS. 157 

erally speaking those metals which are acted upon at ordi- 
nary temperature by dilute acid liberate hydrogen ; but 
when the concentrated acid or elevated temperature is re- 
quired, the corresponding sulphate is usually formed with 
the liberation of sulphur dioxide. This latter result is 
probably due to the decomposition of the strong acid by 
the liberated hydrogen, especially at high temperature. 

The sulphates are an important class of compounds, 
many of them being extensively employed in the arts. 
They are insoluble in alcohol ; as a class they are soluble 
in water, except those of lead and of the alkaline-earth 
metals (calcium, strontium, and barium), and these are 
slightly soluble, except that of barium, which is very 
insoluble in water and only slightly so in acids. The nor- 
mal sulphates are decomposed by heat except those of the 
alkali and alkaline-earth metals and of magnesium, the 
latter only partially decomposing at very high temperature. 
The insolubility of the barium sulphate gives a ready, pre- 
liminary test for the detection of any sulphate in solution, 
which is to add to the suspected solution any soluble salt 
of barium, and if any sulphate be present, a white precipi- 
tate will be formed insoluble in water and dilute acid. 

Pyro-sulphuric Acid or Di-sulphuric Acid. This acid is 
also called fuming sulphuric acid and Nordhausen oil of 
vitriol. Its formula is H^OXH^SO^SOs). It may be con- 
sidered as consisting of a molecule of sulphuric acid and 
one of sulphur trioxide, or two molecules of sulphuric acid 
less one of water. It is now made on a manufacturing 
scale by dissolving sulphur trioxide in sulphuric acido 
This acid was originally manufactured at Nordhausen in 
Saxony, a fact which explains one of its names. The origi- 
nal method consisted in distilling the basic ferric sulphate 
of iron, by which sulphur trioxide was evolved and con- 
densed in a solution of sulphuric acid ; the basic salt 
being obtained by oxidizing ferrous sulphate, by exposing 



158 INORGANIC CHEMISTRY. 

it to a moderate heat in air. This acid fumes in the air 
when the bottle containing it is open, due to the escape of 
sulphur trioxide. It is heavier than the common acid, its 
specific gravity being 1.9. It has important application in 
the preparation of indigo dyes and in the colors obtained 
from coal tar. This pyro-acid was obtained by the last of 
the above processes as early as the fifteenth century. 

Thiosulphuric Acid ; H 2 S 2 3 . This acid was formerly called hyposul- 
phuric acid. It has not been obtained in a free state, being very unstable. 
Its salts, however, are stable and numerous, by far the most important 
being the sodium thiosulphate. This salt is easily prepared by digesting 
powdered roll sulphur with solution of sodium sulphite (Na 2 S0 3 ). The 
latter salt combines with an atom of sulphur, forming the thiosulphate 
(Na 2 S 2 3 ), which may be crystallized from the solution. This is the salt 
so largely used in photography and commonly called hyposulphite or 
"hypo." It is also used as a substitute for sodium sulphite as an anti- 
chlore. The acid may be regarded as obtained from sulphuric acid by 
replacing one atom of oxygen by an atom of sulphur; hence the old term 
hyposulphurous is not strictly applicable. 

Hypo sulphurous Acid ; (H 2 S 2 4 ). The solution of this acid has been 
obtained, but it rapidly decomposes. Its salts are more stable than the 
acid. The sodium salt is the most important and is obtained by the action 
of zinc filings upon a concentrated solution of the acid sodium sulphite. 
This salt is used by the dyer and the calico printer, and its formula appears 
to be Na 2 S 2 4 . 

There are several other oxyacids of sulphur whose names and formulae 
are here given : dithionic, H 2 S 2 6 ; trithionic, H 2 S 3 6 ; tetrathionic, H^Oe; 
pentathionic, H 2 S 5 6 . Very little is known of these, and they are of little 
practical importance. 

COMPOUNDS OF CARBON AND SULPHUR. 

CARBON DISULPHIDE ; CS 2 . 

The most important compound of carbon and sulphur 
is the carbon disulphide. The two elements unite directly 
to form this compound when the vapor of sulphur is passed 
over red-hot carbon. 

The disulphide is prepared on a manufacturing scale by 



NON-METALS. 159 

heating carbon in a large vertical earthenware or iron re- 
tort, the sulphur being admitted near the bottom of the 
retort. The retort is built in a suitable furnace for obtain- 
ing uniform temperature. The vapor of sulphur combines 
with the heated carbon, and the carbon disulphide produced 
passes by a pipe from the upper part of the retort to the 
condensing arrangements. 

Properties. Carbon disulphide is a clear mobile liquid, 
of great refractive power. When pure its odor is not dis- 
agreeable, but as usually met with the liquid is decidedly 
fetid. The repulsive odor is probably due to other volatile 
sulphur compounds, from which it may be freed by agi- 
tating with mercury and redistilling. The specific gravity 
of the liquid is 1.29, its boiling-point 46° C. Its vapor is 
highly poisonous if inhaled in undiluted form; even in 
small quantity it in time produces serious effects. 

It explodes violently when mixed with three times it 
volume of oxygen : 

CS 2 + 30 2 = C0 2 + 2S0 2 . 

It is exceedingly inflammable, its ignition-point in air being 
only 149° C. ; it burns with a pale blue flame characteristic 
of sulphur, yielding C0 2 and S0 2 . The low igniting-point, 
coupled with its explosive properties, the high specific 
gravity of its vapor, and its poisonous properties, make 
great care necessary in manipulating it. Its solvent prop- 
erties are quite remarkable ; among the substances dis- 
solved by it are sulphur, iodine, phosphorus, camphor, 
caoutchouc, oils, and fats. 

Uses. Carbon disulphide is employed for a number of 
useful purposes, the most important of which depend upon 
its solvent power for fats and oils. It is used for extract- 
ing many essential oils from natural sources, seeds, fruits, 
and flowers; for extracting the aromatic principles of spices 
and other substances used as condiments. It is used in 



160 INORGANIC CHEMISTRY. 

preparing vulcanized caoutchouc and in the manufacture 
of rubber goods. On account of its high dispersive and re- 
fractive powers it is used in optical prisms. It is very dia- 
thermic, readily permitting the passage of heat rays; if 
rendered opaque by a solution of iodine, it may be used to 
separate the luminous and non-luminous rays. Its poison- 
ous properties have been turned to account for the destruc- 
tion of weevil in grain, and for the destruction of moths. 

Carbon disulphide forms compounds analogous to those formed by 
carbonic anhydride, the sulphur corresponding to oxygen. It forms a feeble 
acid, H2CS3, analogous to carbonic acid; the corresponding salts are such 
as Na 2 CS 3 , K 2 CS 3 , which are called sulphocarbonates or thiocarbonates. 

Other Carbon Sulphides. Two other carbon sulphides are known, one 
of which is carbon, monosulphide (CS), the sulphur analogue of carbon 
monoxide, the other is thought to have the formula C 3 S 2 . These bodies 
have found no applications. 

SELENIUM AND TELLURIUM. 

Selenium. It is a rare element and much resembles sulphur in its 
mode of occurrence, physical and chemical properties. It has been found 
in the free state, but in very small quantity, associated with sulphur. It 
usually occurs as selenides of the metals together with the sulphides. 
Selenium has been obtained in several allotropic forms, the most distinct 
of which are the varieties which are soluble and insoluble in carbon 
disulphide. 

The crystalline form of selenium is a conductor of electricity, and this 
power is much greater in light than in darkness. This alteration of con- 
ducting power with variation of light intensity has been made use of in 
constructing the photophone, but the instrument has not yet proved of 
practical value. The name Selenium is from the Greek word {2eXr/vrf) for 
moon, the closely resembling element having been called tellurium from 
tellus^ the earth. 

Tellurium. Tellurium is even less common than selenium. It has 
been found native in some gold ores, and in combination with gold and 
some other metals. It has recently been found in masses of 20 pounds 
weight in Colorado. It has the external appearance and lustre of bismuth, 
and in its physical properties more closely resembles the metals than non- 
metals. In its chemical relations it is closely related to selenium, and both 
these elements are connected by strong analogies with sulphur, Both 



NON-METALS. 161 

tellurium and selenium form oxides and oxyaeids analogous to sulphurous 
and sulphuric oxides and the corresponding acids. They also form 
hydracids analogous to hydrogen sulphide, each of the above elements 
replacing sulphur in the respective compounds. Tellurium and selenium 
likewise combine with the chlorine group, and notwithstanding their sim- 
ilarity to sulphur they both form sulphides. 

PHOSPHORUS; P. 

Occurrence. Phosphorus is very widely, though not 
abundantly, distributed in its compounds, but it never 
occurs in a free state. It is an essential constituent of all 
fertile soils. It is necessary to the growth of certain parts of 
the vegetable structures, especially of fruits and seeds. 
From plants used as food the compounds of phosphorus 
pass into the animal body and are essential constituents of 
the juices of the animal tissue, and more especially of the 
bony skeletons of animals, which contain nearly three fifths 
their weight of calcium phosphate. Its compounds are 
found in all sea water, generally in river water, and in many 
springs. It has also been found in meteoric stones. Phos- 
phorus accordingly ranks with carbon, hydrogen, oxygen, 
and nitrogen as one of the elements essential to organic life. 
This element was discovered by Brand in 1668; he obtained 
it from urine. Between 1670 and 1680 it is said to have 
been exhibited to several crowned heads of Europe as one 
of the wonders of nature. (Roscoe and Schorlemmer, 
"Treatise on Chemistry," vol. i.) 

Preparation of Phosphorus. Formerly phosphorus was 
entirely obtained from bone-ash, but now the greater 
cheapness of many of the phosphates of mineral origin has 
led to their use for the manufacture of phosphorus. Other 
things being equal, bone-ash is still the most desirable raw 
material for obtaining phosphorus ; the ash is tricalcic di- 
phosphate, Ca 3 (P0 4 ) 2 . 

Before the introduction of the electric furnace the 
standard method of preparing phosphorus was as follows 



162 INORGANIC CHEMISTRY. 

The calcic phosphate was treated with sulphuric acic\ 
which liberated the tribasic phosphoric acid with produc- 
tion of calcium sulphate. The tribasic acid under the 
application of heat became the monobasic acid. This acid 
was deoxidized by carbon with the liberation of phosphorus 
and formation of carbon monoxide. The changes are indi 
cated by the reactions 

Ca 3 (P0 4 ) 2 + 3H 2 S0 4 = 3CaS0 4 + 2H 3 P0 4 ; 

by mixing with carbon and drying at a low red heat, 

H 3 PO = HP0 3 + H 2 ; 
by distilling the mixture, 

2HP0 3 + C 6 = 6CO + H 2 + P 2 . 

The simplest and most modern method of preparing phosphorus is by 
heating a mixture of calcium phosphate, silica, and charcoal in an electric 
furnace. The gaseous products pass off and the phosphorus is collected 
under water : 

Ca 3 (P0 4 ) 2 + 3Si0 2 + 5C = 3CaSi0 3 + 5CO + 2P. 

This method was proposed many years ago, but at that time it was im- 
practicable commercially because of the high temperature necessary. 
The reduction is brought about by the high temperature and electrolytic 
action does not enter. The alternating current may be employed. 

The crude phosphorus thus obtained is purified by 
fusion and solidification and finally cast into sticks or 
wedges, the entire operation being conducted beneath the 
surface of warm water. The greater proportion of the 
world's supply of phosphorus is made at Wednesfield, 
near Birmingham, England. It is also made in France, 
and at Frankfort and Griesheim, Germany, and in small 
quantities at other places. 



NON-METALS. 163 

Properties of Ordinary Phosphorus.— Ordinary phosphorus 
when freshly made as above described is a translucent, al- 
most colorless wax-like solid. At ordinary temperature it 
is somewhat harder than wax, is flexible and sectile ; at 5.5° 
C. and below it becomes hard and brittle. Even in the 
dark it soon loses its translucency and becomes coated 
with an opaque white film. This action is hastened by the 
light, and by the action of direct sunlight it becomes red, 
due to the conversion into the allotropic red phosphorus. 
It melts at 44° C. It is insoluble in water and usually kept 
immersed in that liquid. It is soluble in naphtha and car- 
bon disulphide. It crystallizes when deposited from solu- 
tion in carbon disulphide. Its specific gravity is 1.83 at 
10° C. 

Exposed to the air phosphorus gives off fumes and 
glows with a faint greenish light ; both these phenomena 
are believed to be due to the oxidation of the phosphorus, 
but are not thoroughly understood. 

It inflames in the air when heated above its melting tem- 
perature, and burns with a brilliant white flame, evolving 
white clouds of P 2 5 . In pure oxygen this combustion is 
intensely luminous. 

The low temperature of the ignition of phosphorus 
renders great care necessary in handling it, to avoid acci- 
dent. It should generally be manipulated under water. 
Ordinary phosphorus is very poisonous when taken inter- 
nally. The vapor is also poisonous when inhaled. Persons 
engaged in manufactures requiring the manipulation of 
phosphorus are often affected by phosphorus poison, very 
frequently resulting in the decay of the bones, especially 
those of the jaws and nose. 

Phosphorus when moist will combine with oxygen, 
chlorine, bromine, iodine, sulphur, and with many of the 
metals. 



164 INORGANIC CHEMISTRY. 

Amorphous or Red Phosphorus. This is tlie principal alio 
tropic form of ordinary phosphorus. When ordinary phos- 
phorus is heated for 49 or 50 hours to 230° or 240° C. in 
ovens, or in an atmosphere that does not act upon it, it is 
converted into a red opaque mass, which is widely different 
from common phosphorus. It is insoluble in carbon di- 
sulphide, is not poisonous, emits no vapor, and does not 
phosphoresce. It cannot be inflamed by friction, and only 
ignites in the air when heated to 260° C. The red phos- 
phorus is much less chemically active than the ordinary 
phosphorus. This difference of action can be strikingly 
shown by placing the two varieties in contact with iodine ; 
the red is unaffected, while the common phosphorus unites 
with the iodine, producing combustion. In the allotropic 
transformation there is no change of weight, though the 
two varieties differ in specific gravity. The specific gravity 
of ordinary phosphorus is about 1.83, that of the red phos- 
phorus is 2.14. 

Professor Schenck of Marburg, Germany, has recently 
produced a new variety of phosphorus, called scarlet 
phosphorus. It is prepared by boiling a solution of 
yellow phosphorus in phosphorus tribromide. It is not 
poisonous, is very stable in the air, but reacts much more 
readily than the red phosphorus. Matches made from it 
have shown great keeping powers, and it is thought that 
the body will prove useful in match preparation, as it 
requires no special ignition surface. 

Uses of Phosphorus. The principal use of phosphorus is 
in the manufacture of matches. It is also used to a small 
extent in the preparation of certain vermin poisons. The 
lucifer matches are made by tipping the splints with sul- 
phur, wax, or parafnne, to surely convey the flame to the 
wood. The match composition consists of phosphorus and 
some oxidizing agent ; those most commonly used being 



NON-METALS. 165 

potassium chlorate, red lead, and lead nitrate. This mix- 
ture is usually bound together and attached to the wood 
by glue or gum. 

The safety matches which cannot readily be ignited by 
ordinary friction have no phosphorus on the match, but 
are coated with a mixture of antimony sulphide and one 
or more oxidizing agents. For ignition the matches have 
to be rubbed on a prepared surface (usually the side of the 
box), which is covered with a mixture containing red phos- 
phorus and fine sand or powdered glass. 

Oxides and Oxyacids of Phosphorus. Four oxides of phosphorus are 
known, the formulae of which are P 2 4 , P2O5, P 4 6 , and P 4 0. The most 
important of these is the P2O5, phosphoric oxide. 

Phosphoric Oxide. This oxide is prepared by burning phosphorus in 
dry air. It constitutes the white fumes which are seen when phosphorus 
burns with flame in dry air. It has a great affinity for water and soon 
deliquesces if left exposed to the air. It is sometimes used as a dehydrating 
agent in the laboratory. It will even extract water from oil of vitriol. 

Orthophosphoric Acid ; H3PO4. This is the compound generally desig- 
nated as phosphoric acid. It is the acid whose salts are usually met with 
in nature as phosphates. The phosphates are indispensable to the growth 
and sustenance of plants and animals. In these compounds phosphorus is 
widely distributed. 

The acid is the final product of the oxidation of phosphorus in the 
presence of water. It may be prepared by boiling phosphorus with nitric 
acid. It can also be prepared from the native phosphates. The acid is 
tribasic. It was formerly used to a considerable extent in calico printing. 

There are several other oxyacids of phosphorus whose names and 
formulae are given in the following table : 

Hypo-phosphoric acid, H 3 P0 2 ; 

Phosphorous acid, H 3 P0 3 ; 

Meta-phosphoric acid, HP0 3 ; 

Pyro-phosphoric acid, H 4 PjO,. 

Other Compounds of Phosphorus. Phosphorus does not combine di- 
rectly with hydrogen, but there are three compounds of these two elements 
known. The most important of these is the gaseous hydrogen phosphide, 
or phosphine, II 3 P. This gas can be prepared in several ways, and will 
generally take fire spontaneously when exposed to the air, but this action 



166 INORGANIC CHEMISTRY. 

appears to be due to the presence of the liquid phosphide, H 4 P 2 , which is 
spontaneously inflammable. The other phosphide, H 2 P 4 , is a yellow solid. 
Phosphorus combines with the halogens, forming two analogous com- 
pounds with each of the elements, chlorine, bromine, and fluorine. It also 
forms two compounds with iodine, but one of these is without an analogue 
among the other halogen compounds. 

ARSENIC; As. 

Occurrence. Arsenic occurs widely distributed but in small quantity, 
and resembles sulphur in its mode of occurrence. It is found native, but 
more generally as the sulphides (realgar and orpiment) and the arsenides 
of the metals. It frequently occurs combined with the sulphides of the 
metals. Arsenic is used only to a small extent. 

Preparation. It is generally prepared in one of two ways : 1. By 
heating arsenical pyrites out of contact with air; the arsenic is distilled off 
and condensed by suitable arrangements. 2. By heating arsenious oxide 
with charcoal ; the oxide is reduced and the arsenic is volatilized and con- 
densed. 

Properties. In its appearance arsenic resembles a metal. It has a 
steel-gray metallic lustre and is a conductor of heat and electricity. Its 
specific gravity is between 5 and 6. It volatilizes without fusing. In dry 
air at ordinary temperature it remains unchanged, but in finely divided 
form it oxidizes in moist air. At a temperature over 70° C. it oxidizes in 
the air and gives off fumes of arsenious oxide, accompanied by a very 
penetrating and characteristic odor suggestive of garlic. When heated to 
a red heat in the air it burns with a bluish-white flame ; in oxygen its flame 
is very brilliant. It is insoluble in water. Pure arsenic does not appear 
to be poisonous, but it may be oxidized after it is taken internally and 
then become a poison. In its chemical properties it is closely allied to 
phosphorus. Arsenic forms no base with oxygen, and hence differs from 
the elements classed as metals. It is used in small quantities to form alloys 
which possess characteristic properties ; it is thus used in the manufacture 
of shot, in bronzing brass, and in other alloys. 

OXIDES OF ARSENIC. 

Arsenic forms two oxides, As 4 6 and As 2 5 . 

Arsenious Oxide ; As 4 6 . This compound is prepared on a commercial 
scale by roasting arseniferous minerals in suitable furnaces or ovens when 
arsenious oxide is the principal product ; arsenical pyrites is usually the 
ore from which it is obtained. The sulphur and arsenic are thus oxidized, 
the former escaping as sulphur dioxide. The arsenious oxide, generally 



NON-METALS. 167 

designated as arsenical soot, is conducted into chambers which expose a 
large condensing surface. The oxide is here condensed to a dark gray 
powder. 

The workmen employed to clear the chambers are clad in leather gar- 
merits with glazed apertures for the eyes, and they breathe through wet 
-cloths. The powder is purified by resublimation and then obtained as a 
white, glistening, crystalline powder. If the crystalline arsenic be sublimed 
under slight pressure at high temperature, white amorphous, vitreous ar- 
senic is obtained. 

Arsenious oxide is obtained in large quantity as a by-product in work- 
ing certain metallic ores, mainly those of cobalt, nickel, silver, and tin. 
It is obtained in large quantities in connection with the tin furnaces of 
Cornwall and Devon. 

The substance commonly known as arsenic in the shops is this oxide. 
It is usually sold in the form of a white powder resembling flour in appear- 
ance but much heavier, its specific gravity being 3.7. It volatilizes without 
fusing. It may be distinguished from any resembling substance by the 
garlic odor emitted when dropped upon glowing coal. This odor is thought 
to be due to a lower oxide. 

Arsenious oxide is a powerful poison; less than three grains have proven 
fatal. The habitual use of it in continually increasing quantities will en- 
able the system to withstand much larger doses. 

The best antidote for arsenic poison as given in the IT. S. pharmacopoeia 
is a mixture of dilute solution of ferric sulphate and magnesia. Carbonate 
of soda may replace the magnesia, and a solution of the perchloride of iron 
may replace the sulphate. Emetics should also be used as promptly as 
possible. This antidote was discovered by Bunsen in 1834. It was a de- 
duction from known chemical facts. Previous to that time no antidote for 
this poison was known. 

Arsenious oxide has many applications, some of which will be men- 
tioned. 

Uses. The oxide is used medicinally to a certain extent. It is some- 
times administered to horses to render their coats smoother. It is used in 
calico printing and in the preparation of certain colors, arsenic being 
present in many pigments. It is used in the preparation of aniline, in 
glass making, as a constituent of white fire in pyrotechnics, as a preserva- 
tive of skins, and in the preparation of various kinds of vermin poison. 

Arsenious Acid. The acid has not been obtained in a free state. The 
solution of arsenious oxide in water, however, yields precipitates with cer- 
tain metallic salts which indicate that the acid is tribasic, ILAsOs. The 



168 INORGANIC CHEMISTRY. 

brilliant Scheele's green is the arsenite of copper (CuHAsOi). The arsenites 
are insoluble or difficultly soluble in water, except those of the alkalies. 
The formulas of the alkaline arsenites indicate that they are derived from 
HAs0 2 . Fowler's solution used in medicine is the arsenite of potassium. 

Arsenic Oxide and Acid. This oxide can be obtained by heating ar- 
senic acid. The acid is prepared by oxidizing As 2 3 with nitric acid under 
proper precautions. 

This acid is largely used as a substitute for tartaric acid in calico print- 
ing and in the preparation from aniline of rosaniline, the magnificent 
magenta dye. 

Arsenic Trihydride. This is the only compound of arsenic and 
hydrogen known. It is always formed when nascent hydrogen and 
arsenious oxide are brought together in acid solutions. It is of importance 
because its production affords a means of detecting the presence of a very 
minute quantity of arsenious oxide. Marsh's test for detecting arsenic in 
cases of poisoning depends upon the production of the gas. The gas itself 
is exceedingly poisonous, and any experiment with it should be undertaken 
with very great care. The chemist Gehlen lost his life by inhaling the gas. 

Sulphides of Arsenic. There are known three sulphides of arsenic, 
the disulphide, As 2 S 2 , the trisulphide. As 2 S 3 , and the pentasulphide, As 2 S 6 . 
The two first named occur native. 

As 2 S 2 , Realgar. This compound occurs native, crystallized in red 
rhombic prisms. It may be prepared by heating arsenic or arsenious oxide 
with sulphur. The form which occurs in nature under the name of 
realgar, red orpiment, is usually prepared by distilling iron pyrites and 
arsenical pyrites together, when the realgar distils over. It is used in the 
manufacture of the Bengal signal lights and Indian fire. In the air it 
burns with a blue flame; with nitre it gives a brilliant white light. 

The Bengal lights are composed of a mixture of 24 parts of potassium 
nitrate, 7 of sulphur, and 2 of realgar. 

As 2 S 3 , Yellow Orpiment. This compound occurs native crystallized in 
yellow rhombic prisms. It may be prepared by heating arsenic with the 
proper amount of sulphur. 

The paint known as King's yellow is a mixture of yellow orpiment and 
arsenious acid, and is of course poisonous. 

The pentasulphide is of less importance than the other two. 

Compounds of Arsenic with the Halogens. Arsenic forms but one 
chloride, the trichloride, AsCl 3 . It forms analogous compounds with bro- 
mine, iodine, and fluorine. It also forms a dicarbide. 



NON-METALS. 169 

ARGON AND HELIUM. 

Argon. This body was very recently discovered. Lord Rayleigh had 
found that the specific gravity of chemically pure nitrogen was not the 
same as that of the nitrogen of the atmosphere. This led to the examina- 
tion of the atmosphere and to the discovery that it contained a substance 
not previously recognized, amounting to nearly one per cent. By the com- 
bined efforts of Lord Rayleigh and Professor Ramsey the substance was 
isolated in 1894. The new body was named Argon (signifying without 
work) in allusion to its chemical inactivity. The investigations up to this 
time indicate that argon is an element with density of 20, referred to 
hydrogen. It appears to be monatomic, and hence its atomic weight 
would be 40. It has been liquefied and solidified by great cold and pres- 
sure. It has, up to this time, resisted all attempts to cause it to combine 
with other bodies. Professor Ramsey therefore thinks that it may be non- 
valent or incapable of forming compounds, and consequently could not 
really be said to have an atomic weight. 

Helium. The existence of this body has been inferred for a consid- 
erable time, through the existence of a bright line in the solar spectrum, 
not attributed to any known body. In seeking for a source of argon, 
Professor Ramsey for the first time in 1895 identified helium among 
terrestrial bodies. Helium has since been obtained from the waters of 
certain mineral springs and has been found in small quantity in the 
atmosphere. It is a colorless gas at ordinary temperature and was 
liquefied by Dewar only with great difficulty. It is monatomic and its 
molecular weight from its density is 4. 

Krypton, Neon, Xenon. During the last half of 1898 and the first half 
of 1899 the discovery of a number of new elements was reported. 
Professor Ramsey and his assistant, Mr. Travers, added three new ele- 
ments to the list, all gases ; these are krypton, neon, and xenon. They 
were all obtained from liquid air. Like helium and argon they have not 
been found to enter into combination with other bodies. Krypton has an 
atomic weight of 81.5, neon of 20, and xenon of 128. From their molec- 
ular heats it has been determined that they are all monatomic. They are 
present in the air in very minute quantities. 



CHAPTER III. 

ADDITIONAL GENERAL PRINCIPLES. 

The principles and theories of Chemistry which have so far 
been employed in our study of the subject are capable of very 
great extension and development. Other important principles, 
theories, and conceptions of this extended science have not up 
to this time been referred to at all. In this chapter it is pro- 
posed to make certain statements of principles and theory more 
full, and to introduce a few others which can by brief reference 
be made intelligible to the beginner and which will ,be valuable 
in unifying results observed and in supplying the physical basis 
for conceptions so essential to most minds for easy and satis- 
factory comprehension. 

STATES OF MATTER. 

Matter is generally recognized in only three states of ag- 
gregation : gas, liquid, and solid. Common experience shows the 
wide difference between these states : the most marked of which 
are that a gas distributes itself uniformly throughout the space 
into which it is admitted — however large, its volume varies 
greatly under changes of either temperature or pressure; a 
liquid takes the form of the containing vessel, except the upper 
surface; a solid has definite form and volume independently 
of surrounding bodies. The only physical conception of matter 
possible from its known properties is a discontinuous structure 
of some kind; that is to say, bodies are aggregates of certain 
kinds of individual units. The molecules already defined are 

170 



STATES OF MATTER. 171 

believed to be the units of which bodies are the aggregates, or 
in certain cases groups of the molecules may form the units. 

Kinetic Molecular Theory. Many properties of gases, such 
as the fact that they are readily compressible, that they per- 
meate every part of the space into which admitted, show that 
their molecules are widely separated and in continual motion. 

The kinetic theory of gases assumes that the molecules of a 
gas are separated by distances which are large as compared 
with their own size, and that they are in continual motion in 
straight lines until deflected by collision with the walls of the 
vessel or with each other, that after collision the molecules 
rebound without loss of motion, that is, are perfectly elastic, 
and that the molecules move independently of each other. 

Under the assumptions of this theory, the pressure of a gas 
can be accounted for and is believed to be due to the impact of 
the molecules against the sides of the containing vessel. Like- 
wise the temperature of the gas can be ascribed to the velocity 
of the molecules and is proportional to the square thereof, and 
Avogadro's law follows as a logical deduction. 

Boyle's law states that the volume of a gas varies inversely 
as the pressure, the temperature of the gas remaining constant. 
This action of a gas is readily conceived from a consideration 
of the theory. Let us assume a volume of a gas retained in a 
cylinder by a piston ; suppose the volume to be decreased to one 
half by a motion of the piston, the temperature of the gas not 
changing. The paths of the moving molecules are on the aver- 
age made shorter, the number of impacts against the piston in the 
same time, and consequently the pressure, being doubled. These 
results, however, would hold only for a gas perfectly fulfilling 
the assumed conditions. It is well known that gases follow 
the law of volumes and pressure only approximately, and the 
departures therefrom can be satisfactorily accounted for by 
recognizing, first, the fact that the molecules are not entirely 
independent of each other and do display a tendency to cohere 
and actually do cohere when liquefied; second, that under 



172 ADDITIONAL GENERAL PRINCIPLES. 

great pressures the volumes of the molecules themselves are 
appreciable when compared with the spaces between them. 

Critical Temperature. Under the kinetic theory the critical 
temperature of a gas is that temperature above which the at- 
traction between the molecules is unable to overcome their 
motion of translation, however great the pressure. 

Liquids and Solids under the Kinetic Theory. In the liquid 
state the cohesive action of the molecules is so great that sepa- 
ration from each other takes place only at the surface and the 
released molecules then move about in the space above as 
gaseous particles, with but slight interference with each other; 
this escape from the liquid state constitutes evaporation. 
When the space above the liquid becomes saturated evapora- 
tion ceases; in this state as many molecules re-enter the liquid 
as escape from its surface in each unit of time, so that, while 
exchange still goes rapidly on, there is a condition of equilibrium, 
the liquid receiving as many particles as it sends out. The 
vapor tension of the liquid equals the vapor pressure of the 
vapor. 

In the solid state cohesion between molecules is much stronger 
than in liquids, the former being obtained from the latter by 
cooling and consequent diminution of the velocity of the mole- 
cules, which would tend to overcome the cohesion. Con- 
versely, with increase of the temperature of a solid, the molecules 
acquire greater velocity and at a certain point break from the 
rigid condition and assume the freedom of liquidity: this is the 
melting point or temperature of the solid, and is constant until 
the whole mass is liquid, since the heat absorbed is consumed 
in loosening the molecules and giving them greater freedom of 
motion. 

AFFINITY. 

Cause of Chemical Change. Chemical affinity, in a general 
sense, is the name employed to designate the agency of 
chemical change. The reaction-equations thus far used to 



AFFINITY. 173 

represent chemical changes indicate the phenomenon as a sim- 
pler process than it really is. The ordinary equations indicate 
only in part the initial and final results and the general course 
of the reaction. It is proper here to briefly refer to some of the 
causes which influence the course of a reaction and limit its 
extent. 

Kinds of Reactions. Reactions may for present considera- 
tions be divided into reversible and non-reversible or complete. 
A reversible reaction is one such that the original substances 
may be obtained from the products of the reaction by a slight 
alteration of the conditions. This reciprocal action does not 
obtain in the non-reversible reactions. A great many reactions 
have been found to be reversible, and it is possible that there 
are conditions of experiment under which every reaction might 
become reversible. 

Two arrows pointing in opposite directions (<=£) have been 
generally adopted to indicate reversible reactions; thus, 
AB+CD<=*AC+BD means that the indicated substances in the 
two members may remain in the indicated proportions indefi- 
nitely under the conditions, but that an alteration of certain 
conditions will cause the reaction to proceed in one direction 
or the other, increasing the proportion of the substances on one 
side and decreasing them on the other. 

INFLUENCE OF MASS. 

Reaction Equilibrium. When the conditions above de- 
scribed exist in any reaction it is said to be in a state of equili- 
brium. This state may be altered by a modification of the 
conditions. The most important of these conditions is that of 
the mass of the acting substances. It has been found and 
abundantly shown that the extent to which any reaction will 
proceed depends not only upon the relative attractions of the 
factors which take part in the reaction, but upon the relative 
amounts of these factors that are present. 



174 ADDITIONAL GENERAL PRINCIPLES. 

The influence of mass in reversible reactions has been stated 
in the following law: The extent of the chemical change is pro- 
portional to the product of the active masses into their coefficients 
of affinity. 

The active mass of a substance is the quantity of the sub- 
stance, expressed in equivalent weights, which is contained in 
a unit volume of the chemical system undergoing change. 

The coefficient of affinity is denned as the resultant affinity 
of all the attractions which are effective in producing the re- 
action. Thus, in the double decomposition above indicated, 
AB + CD^AC + BD, the affinity which is efficient in the forma- 
tion of the new substances is a function of the affinities between 
all the bodies present, both simple and compound. 

When a state of equilibrium is reached in a reversible re- 
action it does not follow that chemical action has ceased, but, 
on the contrary, it is believed that the changes in one direction 
are just equal to those in the other, so that the indicated pro- 
portions are unchanged. If the conditions are modified, the 
action will continue in one direction or the other until a new 
state of equilibrium is reached. 

If all other conditions are constant, the chemical action is 
proportional to the product of the active masses. It is evident 
that under such conditions a reaction as above indicated, of 
double decomposition, could never continue to completion if 
all the bodies remain within the sphere of action, for the prod- 
uct of the active masses on the two sides must reach equality, 
since one is increasing and the other decreasing, or the tendency 
to reproduce the reagents is the same as that to produce" the 
products. 

Application of the Law of Mass Action. The law of mass 
action, as above given, is fundamentally adaptable to revers- 
ible reactions, and in such cases has been shown to have the 
widest application in both organic and inorganic chemistry, 
some of the most perfect applications pertaining to the former 
branch. The influence of mass has been recognized in the 



AFFINITY. 175 

greatest variety of reactions, many usually classed as complete 
as well as the reversible, and the law of mass action has brought 
into conformity a large number of previously disconnected 
phenomena. 

The Laws of Insolubility and Volatility — Complete Reactions. 
It has alreadj 7 " been stated that a large number of the most 
common reactions with which we have to deal, consisting of 
double decompositions, are conditioned by the formation of 
volatile and insoluble bodies, and such reactions are practically 
complete. These classes of reactions have been included under 
the general law of mass action, and they proceed to completion 
because one of the products in each case is removed from the 
sphere of action, and is no longer among the active masses. 
The volatile product escapes as a gas and the insoluble body 
separates as a precipitate. 

The case of insolubility is illustrated by the action of a 
solution of a soluble sulphate upon a solution of barium chloride, 
represented by the equation 

BaCl 2 + H 2 S0 4 = BaS0 4 + 2HC1. 

The barium sulphate produced is insoluble and falls as a pre- 
cipitate; the tendency for the reaction to proceed from right 
to left as the relative masses vary, is in the main prevented, 
because the precipitate is in such form that it exerts little 
chemical influence. The law of volatility, under which volatile 
bodies are displaced from their compounds by less volatile, is 
illustrated in the formation of hydrochloric acid by the action 
of sulphuric acid upon common salt, represented by the equa- 
tion 

2NaCl + H 2 S0 4 = Na 2 S0 4 + 2HC1. 

The volatile hydrochloric acid passes off and is removed from 
the sphere of action and the reaction passes to completion. 

In many of the cases ordinarily considered as falling under 
the law of insolubility, the precipitated substance is not abso- 



176 ADDITIONAL GENERAL PRINCIPLES. 

lutely insoluble and is not -removed from the sphere of action, 
and the reaction is not complete. 

Other Complete Reactions. It has already been stated 
that, from the principles of mass influence, an ordinary revers- 
ible reaction of double decomposition can never proceed to 
completion. Such reactions, however, may be made approx- 
imately complete as regards one of the reagents by using a 
large excess of the other. 

There are other instances of reactions which are complete, 
or so nearly so that the reverse change is negligible, and in 
which none of the above conditions exist; as, for example, the 
solutions of 

(NH 4 ) 2 S0 4 and K 2 C0 3 

give a complete reaction, producing 

KjS0 4 and (NH 4 ) 2 C0 3 ; 

again, the indicated reaction 

HCl + NaOH=NaCl+H 2 

is practically complete, although all the products apparently 
remain in the sphere of action. It is probable in such cases 
that the extent of the reaction is determined by the influence 
of the solvent upon the reacting bodies. 

Homogeneous and Heterogeneous Equilibrium. When a 
number of substances are brought together in such a way that 
they are capable of reacting upon each other they constitute a 
chemical system. The system is said to be homogeneous when 
it has the same physical and chemical composition at every point; 
it is a heterogeneous system when this is not the case. Gases 
and homogeneous liquids constitute the first class; if solid sub- 
stances or non-homogeneous liquids are present, the system is 
heterogeneous. 

The law of mass action is applicable to both kinds of equilib- 



AFFINITY. 177 

num. An incomplete homogeneous reaction is represented 
by the equation 

2HC1 + Na 2 S0 4 ^2NaCl + H 2 S0 4 , 

all the bodies being, in dilute solution. It has been found by 
experiment that in this reaction, when equilibrium is reached, 
all the indicated bodies are present in certain proportions, and 
the equilibrium proportions are the same no matter which side 
represents the initial reagents; moreover, the same result is 
reached though we begin with caustic soda, sulphuric acid, and 
hydrochloric acid. 

An interesting example of an incomplete reaction, in a 
heterogeneous system, is illustrated by the action between 
steam and heated iron. If steam be passed over heated iron, a 
reaction expressed by the equation 

Fe 3 + 40H 2 = Fe 3 4 + H 8 

occurs; by passing hydrogen over the heated oxide the iron 
oxide is reduced: 

Fe 3 4 + H 8 =4H 2 + 3Fe. 

Either reaction may be carried to approximate completion 
under such conditions as practically remove the volatile prod- 
uct of the change in each case from the sphere of action. If 
the reagents in either case be heated in a confined space so 
that all the products are retained in the sphere of action of the 
system considered, the reaction is not completed. 

Strength of Acids and Bases. Returning to the reaction 
above given, all the bodies being in dilute solution, 

2HC1 + Na 2 S0 4 ^;2NaCl + H 2 S0 4 , 

it will be observed that when equilibrium is reached all of the 
indicated bodies are present in certain proportions. In other 
words, the base is distributed between the two acids. The 
same result is observed when equivalent quantities of two acids 
with a sufficient quantity of base to neutralize only one of them 



178 ADDITIONAL GENERAL PRINCIPLES. 

are brought together in dilute aqueous solution. The base is r 
in general, distributed between the two acids, and the propor- 
tion of the base appropriated by each acid determines what 
Thomsen has termed the avidities, and what Ostwald terms the 
relative affinities, of acids. 

From numerous experiments involving different pairs of 
acids tables of relative affinities or strengths of a number of 
acids have been determined. In a similar way, by determining, 
the distribution of an acid between two bases the strength of 
bases has been determined. 

By these tests hydrochloric and nitric acids are of the same strength and 
twice as strong as sulphuric acid. The alkaline hydroxides are the 
strongest bases by the similar standard. The term equivalents above used 
is more general than that originally employed, and in the above reaction 
the indicated molecular weights employed are equivalents; i.e., 2HC1, 
H 2 SO,, Na 2 S0 4 . 

The strength of acids measured in this way is different from 
that determined by the heats of combination. These relative 
numbers are not characteristic constants of the respective acids, 
since they are found to \ r ary with the strength of the solutions. 

Solutions. There are various kinds of actions which may 
be termed solutions. 

1st. Solution in Gases. When different gases mix without 
chemical action the term solution is often applied to the mix- 
ture, and in such cases any quantity of one gas can dissolve an 
unlimited quantity of another. Liquids generally give off 
vapor into the surrounding gas and are then sometimes said to 
dissolve in the gas. There are some solids which give off vapor 
(sublime) without becoming liquid and are then said to dissolve 
in the surrounding atmosphere. 

2d. Solution in Liquids. Solids, liquids, and gases all form 
solutions in liquids. 

3d. Solution in Solids. The absorption of gases and liquids by 
solids and the diffusion of solids into each other appears to 
justify the use of the term " solution in solids." 



SOLUTIONS. 179 

The solutions in liquids are the most important of these 
actions. General reference has already been made to these 
solutions and the difficulty of deciding whether they result 
from a simple change in the state of aggregation of the dissolved 
bodies or involve also chemical action. In some cases we are 
compelled to the latter conclusion, but in many others no chem- 
ical action can be proved. 

Terminology Employed Considering solutions in liquids, 
the liquid which forms the bulk of the solution is designated the 
solvent; the other body is called the solute, and the amount of the 
solute dissolved in a specified quantity of the solvent defines 
the concentration. A normal solution contains in a liter (1000 
c.c.) of the solvent a number of grams of the solute expressed 
by its equivalent weight; this number is called the gram- 
equivalent of the solute. 

The equivalent weight of a compound is the amount of it 

which will interact with the equivalent weight of an element. 

The gram-equivalent of the solute is found by dividing its 

molecular weight by the number which shows the hydrogen 

atoms necessary to combine the acid radical of the solute. 

Thus a gram-equivalent of HC1 is 3 4 5 = 36.5, of H 2 S0 4 is 

^=49, of AlCl 3 = 1 f- 5 =44.5. A normal solution of these 

bodies would then contain in a liter 36.5, 49, and 44.5 grams of 

the respective bodies. Solutions are semi-normal, quinti- 

normal, deci-normal, centi-normal, etc., when they contain per 

liter I, 1, tV, or T ^ the weight of the solute. These concentra- 

N N 

tions may be abbreviated respectively to — or .5N, — or .2X, 

N 

— or .IN, etc. A molar solution contains in a liter oi the sol- 
vent the molecular weight expressed in grams o\' the solute; 
this weight, the gram-molecular weight, is termed a mole. 

When the equivalent and the molecular weights of the solute 
are the same, normal and molar solutions are of course identical. 

Theory of Solutions. Returning to the cases o( the solutions 



180 ADDITIONAL GENERAL PRINCIPLES. 

of solids in liquids in which no chemical action appears, it has 
been discovered that many dilute solutions behave as if the 
solute were present in a condition independent of the solvent, 
and this has led to a kinetic molecular theory of solution, which 
states that "the molecules of the solute pervade the solvent 
and possess the same properties that they would possess did 
they alone, in a state of gas, occupy the volume filled by the 
solution." The solute is thus regarded as disseminated by the 
solvent through a larger space, the cohesion of its molecules is 
overcome, and it is practically in gaseous condition, occupying 
the volume of the liquid : the liquid affording the medium or 
vehicle for the transformation of the solid and the diffusion of 
its molecules. We may formulate a physical concept under this 
theory by saying that sugar does not evaporate in air, but when 
placed in water it evaporates or its particles separate from each 
other, and its molecules diffuse throughout the volume of the 
liquid, moving in all directions like gaseous particles. 

Just as a gas diffuses through all the space available to it, 
so, in the cases under consideration, a dissolved substance 
diffuses through all the available solvent. The tendency of 
the molecules of a solid to separate from each other and pass 
into the liquid has been called "solution pressure"; this pressure 
for the same substance varies with different liquids. The 
molecules after release from the solid move in all directions 
through the liquid, and it will be immediately shown that these 
liberated particles exert a pressure in the liquid which is called 
"osmotic pressure" which increases with the concentration of 
the solution. When the concentration and consequently the 
osmotic pressure reach a certain degree, no further solution of 
the solid occurs. 'When this degree of concentration is reached 
the solution is called saturated, and we may accordingly with 
propriety assume that when this occurs the osmotic pressure 
equals the solution pressure. Under this condition the amount 
of the dissolving substance thereafter remains unchanged, but 
this is because the solid receives as many molecules from as it 



OSMOTIC RELATIONS. 181 

loses to the solution, and the exchange of molecules contin es; 
that such is the case can be shown in more than one way. We 
have here an equilibrium between osmotic and solution pres- 
sure analogous to that between vapor tension and vapor pres- 
sure (page 172). 

Osmotic Pressure. If a concentrated solution be left in free 
contact with a quantity of the pure solvent, the dissolved sub- 
stance will eventually distribute itself uniformly throughout 
the whole, forming a less concentrated solution. If the 
pure solvent and the concentrated solution be separated 
by a membrane or diaphragm through which the solvent will 
pass and the solute will not, the tendency of the dissolved sub- 
stance to permeate uniformly the entire volume of the solvent 
and produce a less concentrated solution will still exist, but 
since the dissolved substance cannot pass across the diaphragm 
into the pure solvent, the latter passes into the former; in all 
such cases there then exists a pressure outward from the solute 
side of the diaphragm, which is termed " osmotic pressure," 
so called because it can be made apparent and measured only by 
making use of the osmotic properties of diaphragms and mem- 
branes (page 35). 

The method of measuring osmotic pressure will be found in 
all books dealing principally with physical chemistry. It is 
found that osmotic pressures vary directly with the concentra- 
tion of the solution; that is to say, this pressure is proportional 
to the weight of the solute in unit volume of the solution, just 
as the pressure of a gas is directly proportional to the weight 
of the gas in a unit of volume, and Boyle's law expresses equally 
well the varying relations for both. The osmotic pressure also 
varies r^ of its value at C C. for a change of one degree of tem- 
perature, or varies as the absolute temperature. Gases at high 
concentration (under great pressure) cease to obey the laws of 
Boyle and Charles; the same is true for highly concentrated 
solutions. Boyle's and Charles's laws apply both to osmotic 
and gas pressure, but this shows nothing as to the relative mag- 



182 ADDITIONAL GENERAL PRINCIPLES. 

nitudes of this pressure under comparable conditions, but it has 
been further shown that equal volumes of solutions which have 
at the same temperature equal osmotic pressures contain the 
same number of molecules of the dissolved substances. This is 
a statement of Avogadro's law applied to solutions, and the 
relation was first pointed out by van't Hoff * Finally it is 
found that the osmotic pressure of a substance in solution is 
identical with the gas pressure which the weight of the dis- 
solved substance would exert at the same temperature if it 
were in a state of gas and limited to the volume occupied by the 
solution : or that under the same conditions a particle or mole- 
cule separated by solution exerts the same osmotic pressure 
that a gas particle exerts gas pressure. Thus it may be stated 
that a solution of sugar exerts the same osmotic pressure that a gas 
does gas pressure when the same number of particles of the gas 
are retained in a volume equal to that of the solution. Solu- 
tions which exert equal osmotic pressures are said to be isotonic. 

Effect of Concentration on the Freezing- and Boiling-points 
of Solutions. Other physical properties of solutions besides the 
osmotic pressure are found to vary with and be proportional to 
concentration. The most important of these are the freezing- and 
hoiling-\)omi$ and the vapor tensions of solutions. With regard 
to the first of these magnitudes, the results collated show that 
"when molecular quantities of different substances are dissolved 
in the same amount of a solvent they lower the freezing-point of 
the solvent to the same extent." 

The lowering of the vapor pressure and the consequent raising 
of the boiling-point of the solvent by the presence of substances 
in solution are determined by the same laws as apply to the 
lowering of the freezing-point. 

These properties may be summarized thus : 

* From recently published data it appears that it may be necessary to 
slightly modify this law of van't Hoff so as to read " that the osmotic pres- 
sure of the substance is the same it would exert as a gas at the same tem- 
perature and reduced to the volume of the solvent in a pure state." 



OSMOTIC RELATIONS. 183 

1. Isotonic solutions with the same solvent have the same 
freezing-point; 

2. Isotonic solutions with the same solvent have the same 
boiling-point ; 

3. Isotonic solutions with the same solvent have the same 
vapor tension at the same temperature. 

Determination of Molecular Weights from Osmotic Relations. 
Just as relative molecular weights of gases can be de- 
duced from Avogadro's law, so the relative weights of mole- 
cules of dissolved substances can be found from van't Hoff's 
law, which states that "equal volumes of different solutions at 
the same temperature and osmotic pressure contain the same 
number of molecules of the dissolved substances." The deter- 
mination of molecular weights from the direct relations in 
volved in van't Hoff's law requires the measurement of osmotic 
pressure; this is a difficult operation and not of great accuracy, 
and accordingly not well adapted to the problem involved. 
The other two magnitudes, freezing- and boiling-points of solu- 
tions, are more readily and accurately measured and enable us 
to determine whether solutions contain the same number of 
dissolved molecules in equal volumes. These properties of 
solutions are much used in checking and determining the mo- 
lecular weights of non-volatile bodies, which are necessarily 
excluded from the vapor-density method under Avogadro's 
gaseous law. When the depression of the freezing-point of a 
solvent is used to determine the molecular weight of the solute, 
the method is designated as the "cryoscopic method.'' 

It is to be noted here that the solutions of many classes of 
bodies do not conform to the laws of solutions as above given. 
Thus a dilute solution of potassium chloride gives an osmotic 
pressure nearly twice as great as it should for its accepted molec- 
ular weight, and the depression of the freezing-point of such a 
solution is also nearly twice as great. The determination of 
the molecular weight of this body either by the endoscopic 
method or from its osmotic pressure would give a molecular 



184 ADDITIONAL GENERAL PRINCIPLES. 

weight about one-half that generally accepted and determined 
by analysis. Many other compounds when their molecular 
weights are determined from the properties of their solutions 
are found to be fractions of the weights assigned the molecules 
from other considerations. This anomalous behavior is very 
generally found in inorganic salts, acids, and bases, all showing 
molecular weights too small when determined from the con- 
sideration of their solutions. Dilute organic solutions more 
generally conform to the stated laws of solutions. 

Dissociation by Heat. We have already referred to the 
influence of heat as an agent in chemical change. It is fre- 
quently the cause of the resolution of a body into its com- 
ponents; if the body is reformed upon the withdrawal of the 
heat, the resolution is termed dissociation; if not reformed by 
cooling, it is decomposition. Dissociation is accordingly a 
reversible decomposition. When a body is decomposed in a 
confined space by heat, some of the products being gaseous, the 
decomposition of the body will go on until the liberated gas or 
vapor has attained a certain pressure, greater or less according 
to the temperature. No further decomposition will then take 
place, nor will the elements or constituents recombine so long 
as the temperature and pressure remain constant; but if the 
temperature be raised, the decomposition will begin and con- 
tinue until another definite pressure is reached, when it again 
ceases. If the temperature be lowered, recombination ensues 
until the tension reaches a state corresponding to the lower 
temperature. Such actions are termed dissociation, and they 
belong to the class of reversible reactions, and the amount of 
dissociation produced is conditioned by the temperature and 
active masses of the substances present. 

A simple case of dissociation by heat is that of steam. Steam 
begins to decompose at about 1000° C. ; as the temperature in- 
creases the decomposition goes on until at the temperature of 
2500° C. about half the steam is decomposed into oxygen and 
hydrogen, and no greater amount is decomposed however long 



DISSOCIATION BY HEAT. 185 

the temperature is kept at this point. As the temperature is 
lowered from this point, the separated gases begin to recombine 
and the proportion of the steam to oxygen and hydrogen in- 
creases. At every temperature between 1000° C. and the high 
temperature at which the decomposition of steam would be 
complete, a condition soon exists such that the amount of 
steam decomposed is just equal to that formed by the recom- 
bination of its elements: these are states of equilibrium. 
The relative amounts of steam and oxygen and hydrogen are 
the same at a particular equilibrium state whether the tem- 
perature for that state be reached from above or below. These 
states of equilibrium under dissociation are like the states of 
equilibrium in other reversible actions, not static but dynamic, 
and are analogous to the states of equilibrium between vapor 
tension and vapor pressure and between osmotic pressure and 
solution pressure. .The kinetic theory of gases gives a satis- 
factory answer why a decomposition beginning at a certain tem- 
perature does not complete itself. Under this theory the mole- 
cules are in rapid motion; there is a constant mean velocity for 
the molecules at any temperature; the velocities of the indi- 
vidual molecules may vary on both sides of this mean. By the 
collisions among molecules the atoms are supposed to be dis- 
turbed from their positions of equilibrium in the molecules, and 
when the movement of the molecules becomes sufficiently violent 
the atoms are thrown out of their sphere of mutual attraction 
and decomposition ensues. This only happens to the molecules 
whose velocities are above certain limits, hence there results 
only partial decomposition; partial recombination ensues when 
the atoms set free from unlike elemental molecules enter into 
their sphere of mutual attraction and again unite to form 
compound molecules. 

This dissociation phenomenon explains the departures from 
Avogadro's law found to exist in the determination of molec- 
ular weights from vapor densities. Such departures have 
already been noted in the cases of PC1 5 , NH 4 C1, and other bodies 



186 ADDITIONAL GEXERAL PRINCIPLES. 

(p. 44), and is due to the dissociation of the bodies during the 
determination of vapor densities. Owing to partial or com- 
plete dissociation of such bodies, with corresponding increase 
of volume, their vapor densities and molecular weights result- 
ing therefrom are found to be less than those inferred from 
other considerations. The abnormal results from such bodies 
as just described, at first tended to throw doubt on the law of 
Avogaclro, but the explanations now furnished fully substan- 
tiate the law. The amount of dissociation that a substance 
undergoes is greatly decreased if there be an excess of either 
of the products of dissociation. Thus NH 4 C1 is but slightly 
dissociated in an atmosphere of NH 3 or HC1. This is but an 
illustration of the effect of mass upon chemical action and is 
readily explained from the principles of mass action already 
given. 

Dissociation by Solution. We have seen that the particles 
of certain dissolved bodies exert a pressure in the solvent, 
" osmotic pressure," also that these particles are very probably 
the molecules of the solute. We have also seen that the bodies 
in solution behave precisely as gases occupying the volume of 
the solvent, so that van't HofFs law of osmotic pressure, "that 
equal volumes of different solutions, at the same temperature 
and pressure, contain the same number of molecules," as 
already observed, is an Avogaclro law for solutions. It has 
been pointed out that the molecular weight of certain bodies 
as determined from Avogadro's gaseous lav: are too small, and 
this anomaly was found to be due to dissociation of the body 
by heat during vaporization; similarly the molecular weights 
of certain classes of substances as determined from van't HofFs 
solution law are too small, and there is little doubt that the 
anomaly in the latter case is due to dissociation in solution. 

If osmotic pressure is due to the particles in solution and 
depends upon the number of molecules of the substance dis- 
solved, and this latter is clearly established by many solutions, 
it is evident that abnormally high osmotic pressures, under the 



DISSOCIATION BY SOLUTION. 187 

same temperature and volume, mmst be accounted for by in- 
crease in the number of particles in the solution, and this can 
only come from a splitting up or dissociation of the molecules 
which enter the solution. 

The Nature of Solution-dissociation. Under the above con- 
clusion that many bodies suffer dissociation in solution the ques- 
tion at once arises as to the parts into which the molecules are 
separated, where the plane of separation passes in the different 
molecules. It has already been stated that the abnormal pres- 
sures are generally observed in the aqueous solutions of acids, 
bases, and salts. Our studies have shown us that in all meta- 
thetical reactions taking place in aqueous solutions of these 
same bodies the atoms not only change places with each other, 
but one atom exchanges place with a group of another kind, or 
groups of different kinds of atoms exchange with each other. 
These proportional amounts of the same elements entering com- 
pounds and being capable of transfer from one compound to 
another led to a formulation of the substances in such way as 
to indicate the units which exchanged places; these units which 
were either atoms or groups of atoms we called radicals (p. 21). 
The invariable units of exchange enabled us to make a list of 
the interchanging radicals and to class them as elementary or 
compound. The proportions of the respective elements in the 
compound radicals are as fixed and definite as the atomic 
weights themselves. The results of many metathetical re- 
actions show that the exchanging radicals in aqueous solutions 
of inorganic salts, acids, and bases are H, K, Na, NH 4 , Cu, CI, 
C0 3 , S0 4 , N0 3 , OH, etc. The investigation of the properties 
of solutions (osmotic pressure, freezing-point, vapor tension, 
etc.) indicate that these same radicals are the products of the 
dissociation of bases, acids, and salts in aqueous solution, for 
the properties of these solutions show that they depart from 
the normal two or more times just in proportion as the mole- 
cules of the body contain two or more of these radicals. For 
instance, with dilute solutions of binary compounds like HC1, 



188 ADDITIONAL GENERAL PRINCIPLES. 

KG, etc., there are nearly twice as many particles present in 
the solution as would correspond to the number of molecules 
of the substances dissolved; similarly with solutions of HN0 3 , 
KN0 3 , NaCl, etc. Substances like H 2 S0 4 , CaCl 2 , Na 2 S0 4 , etc., 
give results approximating to three times the number of the 
dissolved molecules of the substances. The more dilute the 
solutions the more nearly the physical properties of the solutions 
accord with the number of radicals present in the solute. 

From these fundamental considerations of the interchanging 
radicals in metathetical reactions and of the physical properties 
of aqueous solutions it has been concluded that the dissociation 
which takes place in solution separates the molecules of the 
solute into its acid and basic radicals, and that these radicals 
each exert osmotic pressure precisely as did the normal 
molecule. 

The Ionic Theory. In consequence of this dissociation in 
solution by which the molecules are separated into parts which 
correspond in composition to radicals, elementary or com- 
pound, we have a new class of substances, some of which are 
known only in solution-dissociation and others show properties 
not shown by the same substance apart from these solutions. 
Thus the dissociated hydrogen of HC1 in solution differs widely 
from the gas in common form, and N0 3 , S0 4 , and C0 3 are not 
known apart from these solutions. These new units brought 
about by solution dissociation are called ions, and the process 
of dissociation into ions is termed ionization (and the term 
"ionogens" has been proposed and partially adopted for the 
bodies susceptible of ionization). That bodies in the ionic form 
have very different properties from those displayed by them in 
ordinary condition will be appreciated from the following con- 
siderations. Hydrogen is the only element common to all 
acids, and it is accordingly essential to acidity, conferring the 
properties usually called acid — sour taste, effect on litmus, etc. — 
yet in the common form it has none of these properties. Com- 
mon hydrogen is very slightly soluble in water, whereas the 



DISSOCIATION BY SOLUTION. 189 

dissociated hydrogen exists only in solution. Again, in a solu- 
tion of KG we have ionic potassium present in water without 
action thereon. The supposed explanation of these newly dis- 
covered properties will be referred to in a later paragraph. From 
the fact already stated, that the more dilute the solution the 
more perfect the ionization, and that as the solvent is removed 
the ions reproduce the parent molecules, until finally by re- 
moving all the solvent the normal substance is entirely restored, 
we are enabled to conclude that solution-dissociation is a rever- 
sible action and a case of true dissociation, the molecules split- 
ting into ions until a state of equilibrium is reached, as in other 
reversible reactions. This reversible action with states of 
equilibrium varying with the quantity of the solvent explains 
the fact already referred to, that the qualities of a solution, 
connected with osmotic relations, do not indicate as wide a 
departure from the normal as the number of radicals in the 
molecule of the substance would demand. For instance, a 
gram-molecular weight of HC1, NaOH, or KG dissolved in a 
liter of water does not exert quite twice the osmotic pressure of 
a gram-molecular weight of sugar (or other substance which does 
not dissociate in aqueous solution), nor does a gram-molecular 
weight of Na 2 S0 4 dissolved in the same volume of water exert 
three times the pressure of the sugar solution. The reason that 
all the ionic radicals present in the substance do not exert pres- 
sure is because all the molecules of the substance dissolved are 
not dissociated. Dissociation only takes place until an equilib- 
rium is established between the original molecules and their 
resulting ions; in the cases mentioned above we should have the 
following actions taking place: HCh=£H + G, NaOFMNa + HO, 
KCfc±K + Cl, Na 2 S0 4 ^±Na + Na + S0 4 . In these cases the 
greater proportion of the molecules are dissociated, but not all. 
Reference has several times been made to the fact that it is 
only ionogens, or acids, bases, and salts which dissociate in 
solution, but it should be noted that the capacity to form ions 
depends not only upon the body dissolved but upon the solvent ; 



190 ADDITIONAL GENERAL PRINCIPLES. 

the influence of the solvent is referred to as its " dissociative 
power." Water has the highest dissociant power; formic acid, 
methyl and ethyl alcohol are fairly strong dissociants. Chloro- 
form; toluene, benzene, and several other organic compounds 
lack dissociant power entirely, no matter what the solute may 
be; again, certain substances, like sugar, show no evidence of 
dissociation in any solvent. 

Electrolys and Electrolytic Conduction. The theory of 
dissociation in solution finds additional and strongest support 
in " electrolysis." This term is applied to the decomposition 
of a substance which takes place when an electric current is 
sent through it or its solution. Any compound which can be 
thus decomposed is called an " electrolyte." Experiment shows 
that it is only ionogens, or the substances which show dissocia- 
tion by the qualities enumerated above, whose solutions con- 
duct electricity and are electrolytes. The solutions of these 
same ionogens in other solvents which give no evidence of dis- 
sociation do not conduct electricity — the solution of other 
bodies than ionogens, as sugar, etc., in any solvent, are non- 
conductors. To fully appreciate the facts here stated we must 
remember that the best dissociant (water) and the substances 
dissolved in it are, by themselves, non-conductors of elec- 
tricity, but the solution conducts very well. This electrolytic 
conduction now finds complete and satisfactory explanation in 
the assumption that the same ions into which the substance is 
dissociated by solution become carriers of electricity and render 
the solution a conductor. 

A full account of the facts and experiments upon which this 
theory rests cannot be given here, but a sufficient number of 
the well-established conclusions to permit a clear comprehension 
of the theory will be inserted. The physical conception of the 
process of conduction is that the different kinds of ions of the 
substance which result from the dissociation by solution are 
the carriers of the electricity. During electrolysis, assuming a 
particular direction for the flow of the current, and that it 



DISSOCIATION BY SOLUTION. 191 

enters the electrolyte through platinum plates, called electrodes, 
immersed therein, then the plate at which it enters is the anode, 
and the one at which it leaves the electrolyte is the cathode. 
During the action, if there be no secondary actions, one set of 
the ions into which the substance is dissociated appears at the 
anode and the other set at the cathode; the products of reac- 
tion appear only at the electrodes. Thus the electrolysis of 
HC1 yields H at the cathode and CI at the anode; if the current 
be passed through a solution of silver nitrate, AgN0 3; the silver 
deposits at the cathode and the radical N0 3 interacts with the 
water, producing HN0 3 and liberating oxygen at the anode. 
With a solution of KN0 3 , hydrogen appears at the cathode and 
oxygen at the anode, but in this case the ionic radical K 
reacts with the water liberating H, and the N0 3 reacts with the 
water as in the case of silver nitrate. The various illustrations 
of electrolysis prove that the same radicals of acids, bases, and 
salts which interchange with each other in metathetical re- 
actions and whose presence by dissociation is clearly indicated 
in the solutions of these bodies are here delivered at the elec- 
trodes of the battery. In nearly all cases secondary actions 
occur at the electrodes, so that the ionic radicals of the solute 
are not themselves liberated. Those ions which travel toward 
the anode are called anions and those which travel toward the 
cathode are cathions. 

It is a long-established fact that the ions liberated in any 
cell are always in the proportion of their chemical equivalents, 
and the same proportions are set free by the same current no 
matter through how many decomposing cells the current passes; 
also the amount of an ion liberated is proportional to the quan- 
tity of the current which has traversed the cell. The above 
statements embody Faraday's law of electro lysis. 

Under the view-point of electrolytic conduction the ions 
travel toward the electrodes. This migration of ions can be 
made perceptible when the ions are colored or when they can 
be made to take part in visible chemical actions along the 



192 ADDITIONAL GENERAL PRINCIPLES 

traveled path. The relative and actual speed of the migrations 
of different ions have been determined under specified condi- 
tions. 

Electrolytic Dissociation. Under the above conception of 
conduction no explanation has been given as to why the ions 
migrate toward the electrodes, nor how it is possible for these 
elementary ionic radicals, like Na, H ; etc., to show such different 
properties from elemental bodies themselves, nor why such 
radicals as N0 3 , S0 4 , C0 3 , etc., exist in these conducting solu- 
tions and not apart from them. These questions are satis- 
factorily met by the assumption that in dissociation the sub- 
stances are separated into electrically charged parts, and that 
ions are chemical units bearing in addition or combined with 
electric charges; it is this combination that gives us the new 
classes of bodies so different from the same chemical units 
without the charges. With this addition to the dissociation 
theory we may explain the migration of the H and other cath- 
ions toward the cathode, because these ions carry a positive 
charge, and the cathode itself is negatively charged or at a nega- 
tive potential by connection with the source of current. The 
anions move toward the anode because they carry negative 
charges, and the anode is positively charged by connection 
with the battery or source of current. While combined with 
these charges the radicals are ions and have properties which 
the same chemical units would not otherwise possess; thus, 
ionic hydrogen confers the acid property which we observe in 
acid solutions; ionic Na, K, N0 3 , S0 4 , etc., are capable of exist- 
ence in water. When these tons deliver their charges to the 
electrodes they return to mere chemical units and display the 
ordinary properties of such units, the hydrogen atoms uniting 
with each other to form hydrogen gas, Na, K, and the acid 
radicals enter into secondary reactions as already described. 

Conclusions. Nature of Electrolysis. From the above 
theory of solutions it is evident that in electrolysis the ionogens 
are not torn asunder by the electric current, but they are 



DISSOCIATION BY SOLUTION. 193 

already ionized by solution. The electric field established be- 
tween the electrodes of the battery merely draws the oppo- 
sitely charged ions of the ionogen to the electrodes; then the 
charges of the ions neutralize equivalent quantities of elec- 
tricity of the electrodes, which causes current from the battery 
to recharge the electrodes. The pressure or voltage of the 
electric field between the electrodes need only be sufficient to 
move the free ions; and this is proven by the fact that the 
smallest voltage accomplishes some electrolysis, but every de- 
composition to continue requires a minimum voltage sufficient 
to overcome all polarization and. the friction of the moving ions. 
It is seen, too, that conduction across the solution is by convec- 
tion, and that these convection charges are already present in 
the solution and are not given to the ions from the battery 
supply. Again, since the solution remains electrically neutral 
and since the ions liberated are invariably chemical equivalents 
of each other, and since their liberation results merely from 
giving up their electric charges to the electrodes, it follows that 
chemical equivalents carry equal charges, otherwise the solution 
would become charged either positively or negatively. We can 
consequently assert that all monadic ions carry equal charges, 
and other ions greater charges in proportion to their valencies. 
This relation of chemical equivalency between liberated materials 
extends throughout the circuit no matter how many electro- 
lytic cells are involved; it includes also the changes which take 
place in the battery itself, which may be considered as the 
director of the system. 

Results of Ionization. We are now prepared to state that 
ions are atoms or groups of atoms brought about through dis- 
sociation of ionogen molecules by certain solvents, water pos- 
sessing the greatest dissociant power. Each ion bears or is 
combined with an electric charge, either positive or negative. 
and every molecule gives two kinds of ions oppositely charged; 
the electric charge is an essential constituent of the ion. The 
ions differ widely in properties from the substances which are 



194 ADDITIOXAL GEXERAL PRINCIPLES. 

of the same composition less the charge; when they lose their 
charges they do not differ from non-ionic substances of the 
same material when such are known. 

Notation and Nomenclature of Ions. A convenient nota- 
tion and nomenclature for these newly recognized substances 
has been suggested as follows : To indicate the ions whose com- 
position involves a plus electric charge a dot (•) is employed; 
for the negative charge a dash (') is employed; the number of 
these symbols typify the number of charges borne by the ion. 
Thus the following symbols stand for the ions of the respective 
elements and compounds: H', N", Ca, Fe, Fe,' CI', SO/', NO/ r 
etc. The ions formed from one molecule always show the same 
number of dots and dashes. The nomenclature proposed, is, 
that for the cathions the termination ion be added to the stem 
of the word, with a prefix to show the valency when necessary; 
for the anions the termination to be anion, osion, or idion, 
according as the anion is derived from an ate, ite, or ide salt; 
thus we should have 

Hydrion for H" Chloridion for CI' 

Sodion " N Sulphidion " S" 

Dicuprion " Cii Hydroxidion " OH' 

Triferrion " Fe" Sulphosion ll SB/' 

etc. Sulphanion " SO/' 

Nitranion " NO/ 

Electrolytes in Solution. The results of ionization show us 
how inaccurately the ordinary formulae represent the condition 
and results of solution. After solution the ionogen is disso- 
ciated to an extent depending upon the substance itself, the 
quantity, nature, and temperature of the solvent. Instead of 
simply the solvent and original ionogen, there are at least two 
other substances in the solution, each of which may affect its 
properties. Under the notation just given the condition of any 
ionogen, as HC1, KOH, CuS0 4 , NH 4 N0 3 , etc., in solution are 
expressed in the form of reversible reactions, a condition of 



DISSOCIATION BY SOLUTION. 195 

equilibrium existing between the ions and the undissociated 
molecules of the ionogen; thus, 

NaClrfNTa + CI HC1<=>H + CI 

KOH<=>K + OH CuS0 4 ^Cu + S0 4 

NH 4 N0 3 <=>NH 4 +N0 3 

The relative quantities of the ions and of the normal molecules 
in the solution when equilibrium is established vary widely for 
different ionogens. The proportions of the molecules of some 
of the common reagents dissociated in normal solutions at 18° 
are given below: 



Nitric acid 


.82 


Potassium hydroxide 


.77 


Hydrochloric acid 


.78 


Sodium 


.73 


Sulphuric acid 


.51 


Barium ' ' 


.69 


Acetic acid 


.004 


Ammonium 


.004 


Carbonic acid (N/10) 


.0017 


Sodium chloride 


.68 


Potassium nitrate 


.64 


Cupric sulphate 


.22 



Independence of Ions. The ions comport themselves as 
independent bodies except that the same number of negative 
and positive ions from the same substance are always present. 
The number of either kind cannot be increased above the other 
by diffusion or any other process. 

The same cathion always displays the same properties no 
matter from what substance it is derived by dissociation, that 
is, no matter with what anion it is associated; thus cuprion 
(Cii) shows the same color whether resulting from the disso- 
ciation of Cu(N0 3 ) 2 , CuS0 4 , or CuCl 2 ; similarly the same anion 
shows the same color whatever be its dissociated cathion. 
Hydrion (H") is one of the ions of all acids and confers upon 
them all the acid properties, which give sour taste, affect litmus, 
etc. Hydro xion (OH 7 ) is present in all alkaline solutions and 
gives them their taste and feel. If chloridion (XT) be one of 
the ions, from any soluble chloride whatever, it has always the 



196 ADDITIONAL GENERAL PRINCIPLES. 

same properties, one of which is its readiness to react with 
argention (Ag*) and to form silver chloride whenever a soluble 
chloride meets a soluble silver salt in solution. Other bodies 
which contain chlorine, as chloroform (CHC1 3 ), potassium 
chlorate (KC10 3 ), etc., which do not yield chloridion do not 
interact with silver nitrate. TTe see then that the presence of 
chlorine as a constituent in a solution cannot in all cases be 
determined by the silver test, but the presence of the chloridion 
can be so determined. The action above described would be 
thus represented: Common salt (XaCl) in solution gives (1) 
NaCl^Na'-J-Cl'*; adding a solution of silver nitrate gives (2) 
AgX0 3 ^Ag--XO/*. 

The several term? of the second members then interact in 
accordance with the formula (8) Ag'+Cr<=»AgCl*; the asterisk 
in each case indicates in which condition the larger number 
of molecules is left after equilibrium is reached. In (1) and (2) 
the much greater portion of the molecules are dissociated; in 
(3) the dissociation is very slight. To explain still further, the 
silver chloride, being very slightly soluble, would be formed and 
precipitated and thus removed from the sphere of action, and 
the ions CI' and Ag 1 would be removed from the solution as 
soon as formed. The continual removal of these ions would 
destroy the equilibrium between the undissociated molecule of 
NaCl and AgX0 3 and their ions, so that the dissociation would 
continue and the result in solution would be finally represented 
by the formula (4; XaXOs^Xa* — X0 3 '*, in which only a small 
proportion of the sodion and nitranion have combined to form 
molecules of sodium nitrate. If all the water should be evap- 
orated, then the sodium nitrate would exist in molecular con- 
dition. 

Similarly, whenever sulphanion (SO/0, one of the ions of 
soluble sulphates, is present it interacts with barion (Ba"), one 
of the ions of a soluble barium salt, precipitating always barium 
sulphate; this action may be represented by the following 
f ormulse . 






DISSOCIATION BY SOLUTION. 197 

Na 2 S0 4 <=> Na- + Na« + SO/'* 
+ + + 

Ba(N0 3 ) 2 *± N0/+ N0/+ Ba"* 

ti u n 

NaN0 3 NaN0 3 BaS0 4 

Final products are shown by the vertical columns of symbols. 
The larger proportion of the molecules of NaN0 3 would be 
dissociated, while the BaS0 4 would be very slightly so ; with the 
entire removal of the solvent (water) both the NaN0 3 and BaS0 4 
would be left in molecular condition. 

Simplification of Analysis. A great number of the more 
common chemical bodies (acids, bases, and salts) are inogens 
and in solution each, in general, gives but one anion and one 
cathion, and when these are identified the salt from which they 
are derived is known. The simplicity which the independence 
of ions introduces into analysis is appreciated when we con- 
sider that four anions and four cathions might give sixteen 
salts by combination in pairs; to decide which of these sixteen 
salts is present it is only necessary to discover which two of the 
eight ions are -present. This simplification has long been used, 
for it has long been known that salts of a particular metal in 
solution give reactions independently of the acid radicals in 
combination, and that acids give reactions independently of the 
metallic radical in combination. The theory of dissociation 
formulates scientifically the relations which experience has 
established. At the beginning of this paragraph it was stated 
that "in general" an ionogen gives but two ions in solution, 
but with certain salts the solvent (water) is itself slightly dis- 
sociated and its ions interact with those of the dissolved salt. 
In such cases the possible components of the solution are more 
numerous, due to the ions of the water, and the combination 
of these with the ions of the salt. 

Salts, Acids, and Bases. A descriptive definition of these 
bodies has already been given, and their interaction in met a- 



198 ADDITIONAL GENERAL PRINCIPLES. 

thetical reactions described, but the definitions become more 
distinct under the ionic theory. 

Salts are compounds which in solution separate wholly or in 
part into anions and cathions; both the anion and the cathion 
may be simple or composite, as in KG, NH 4 C1, NH 4 NO , and 
KN0 3 . The elements which give elementary cathions are metals, 
but non-metals may be present in a composite cathion, and 
metals may be present in composite anions. Acids are ion- 
ogens in which the cathion is always an hydrogen ion, and a 
strong acid is one which contains numerous hydrogen cathions 
in a unit of volume, for the characteristic properties of acid 
solutions depend upon the hydrogen ions. 

Bases are ionogens in which the anions are hydroxyl ions, 
and a strong base contains a large number of hydroxyl ions in 
a unit of volume, and the characteristic properties of bases 
depend upon these ions. The term salt as above defined evi- 
dently includes the acids and bases, acids being salts in which 
the cathions are Irydrogen ions; bases are salts in which the 
anions are hydroxyl ions. Thus under the electrolytic theory, 
as under the purely chemical, acids are hydrogen salts, and 
hydrogen stands in line with the metals under both theories. 
Acidity and basicity of solutions respectively depend solely upon 
the amount of hydrogen and hydroxyl ions present. Hy- 
drogen and hydroxyl are components of water, but since water 
ordinarily does not ionize it is a salt and shows neither acid nor 
basic properties. 

Neutralization of Acids and Bases. When solutions of acids 
and bases are brought together in certain proportions the mix- 
ture shows neither acid nor basic properties and accordingly has 
neither hydrogen nor hydroxyl ions present; the mixture is 
therefore neutral to litmus, both acids and bases being con- 
sumed. A typical reaction in such case is represented by the 
formula HCl + NaOH=NaCl + H 2 0. From what has receded 
we know that when the reagents of the first member are brought 
into solution dissociation takes place until there is an equi- 



DISSOCIATION BY SOLUTION. 199 

librium established between the original molecules and their 
ions. In normal solutions about f or slightly more of the mole- 
cules are ionized and equilibrium in the solutions of these salts 
may be indicated thus: HCh=±Cl' + H* NaOH<r>Na* + OH'* 
When two such solutions are mixed, since water ionizes only 
very slightly its ions, when brought together, unite to reform 
water. This removal of the water ions destroys dissociation 
equilibrium between the molecules of HC1 and NaOH and 
their ions and thus continues the dissociation until only the 
molecules and ions of NaCl remain in the solution. The process 
of such reactions may be represented as follows, in which R 
and M stand for the acid and metallic radicals: 

HR<^R' + H-* 
MOH<=±M' + OH'* 

Ti Tl 
MR H 2 

The interaction indicated horizontally continues until the 
first members disappear; the interaction in the vertical direc- 
tion continues until all the hydrogen and hydroxyl ions have 
united to form water; the action between the other metallic 
and non-metallic ions continues until equilibrium is estab- 
lished between these ions and the molecules of the salt formed 
by their union, and there remains in the solution water, the 
metal ion and the non-metal ion, and a small per cent of the 
undissociated salt. The acid or basic properties of the solution 
disappear or neutralization results when there are no hydrogen 
or hydroxyl ions left in the solution, that is, when the dissociated 
hydrogen ions from the acid are the same in number as the 
dissociated hydroxyl ions from the base, for in such cases these 
ions combine to form water and the solution is neutral. 

The above general formula may be used to indicate the inter- 
action in all cases of acids and bases, and the neutralization is 
brought about by the union of the hydroxyl and hydrogen ions 
-and may in all cases be expressed by the equation H + OH =H 2 0. 



200 ADDITIONAL GENERAL PRINCIPLES. 

Heat of Neutralization. In the case of the active acids and 
bases, or those which in dilute solutions are very highly ionized, 
practically all the hydrogen and hydroxyl ions combine to form 
water. This theory gives a reasonable and satisfactory ex- 
planation of the fact that "dilute solutions of gram-equivalent 
weights of the active acids and bases produce the same quantities 
o] heat," viz., that due to the combination of the hydrion and 
hydroxidion resulting from the dissociation of the acids and 
bases; because gram-equivalents of these ionogens contain the 
same amounts of hydrion and hydroxidion, and all the heat 
in each case is due to the combination of these ions. This 
conception is indicated by the following equations in which the 
complete- dissociation of the acids and bases in solution is in- 
dicated : 

HC1 = H + CI', HN0 3 = H • + N0 3 , NaOH = Na* + OH'. 

When solutions of the acids and bases are brought together the 
action between the dissociated ionogens is supposed to be as 
follows: 

H- + CI' + Na- + OH' =Na- + CI' + H 2 0, 
H-+N0 3 ' + Na- + OH'=Na- + N0 3 ' + H 2 0. 

The heat set free is the same in each case, since equivalent 
quantities of hydrion and hydroxidion react. The cathion of 
the sodium and the anions of the acid radicals remain in solu- 
tion; if the solution be concentrated by evaporation, sodium 
chloride and nitrate will be found as the result of neutralizing 
sodium hydroxide solution by HC1 and HN0 3 . 

Ionic Conduction of Electricity. Under the conception of 
electrolytic dissociation it has been stated that the ions are 
carriers of charges between the electrodes during the electroly- 
sis of any ionogen. We should accordingly expect to find that 
when equivalent solutions are placed under like conditions 
their conducting power would depend both upon the num- 
ber of the ions and their migrating speed; in other words, that 



DISSOCIATION BY SOLUTION. 201 

the most highly dissociated acids with numerous speedy hydro- 
gen ions would be the best conductors. And such is the case; 
the solutions of strong bases are second in conducting power; 
metallic salts, although highly ionized in solution, conduct less 
well because their ions move more slowly. Under the ionic 
theory of conduction the degree of dissociation may be com- 
puted when the conducting power of different solutions and the 
relative speed of each kind of ion is known. The degree of 
ionization computed by conducting power coincides with that 
found from considerations of abnormalities of freezing, boil- 
ing-points and osmotic pressure of the same solutions. 

Summary. The principal lines converging to the support 
of the theory of dissociation in solution. 

1st. The conducting power of the solutions of ionogens. 

2d. The parallelism of behavior of electrolytes and gases or 
osmotic pressure phenomena. 

3d. The abnormal lowering of freezing or raising of boiling- 
points by electrolytes in solution. 

4th. The identity of heats of neutralization of equivalent 
solutions of acids and bases. 

5th. The fact that chemical reactions are generally so slight 
between dry electrolytes or when dissolved in non-dissociant 
liquids. While the evidence in support of the theory is very 
strong it is proper to state that a number of experimental facts 
have not yet been brought into harmony with the theory. 

Thermochemistry. In the previous discussion of chemical 
processes only the transformations of matter have been con- 
sidered, but these processes, besides involving a change in the 
distribution of matter, involve also a change in the distribution 
of energy. Matter unassociated with energy is not known to 
us, and energy like matter can be neither created nor destroyed. 
Energy exists in many forms, as kinetic or potential, as heat, 
light, electrical energy and chemical energy. All these forms 
can be converted the one into the other, so that definite forms 
of the one correspond to definite forms of the other. 



202 ADDITIONAL GENERAL PRINCIPLES. 

Chemical energy is that form of energy produced during 
chemical action and is the least understood of the different 
forms; neither it nor its factors can be directly measured. 
Chemical energy is generally transformed into heat. Thermo- 
chemistry treats of the thermal changes produced by chemical 
processes. These changes may result in external work as well 
as in changes of temperature. 

Under the present conception of the atomic and molecular 
constitution of matter, all chemical changes must be conceived 
as associated with the movement of material particles and thus 
involving mechanical considerations. We know that the 
equilibrium of every chemical system is dependent upon other 
conditions than the matter present. The other, commonly 
recognized, principal influencing factors are heat, light, elec- 
trical energy, and pressure. On the other hand, every chemical 
change is accompanied with a development of one or the other 
of these forms of energy. A redistribution of energy in the 
system produces a chemical change, and a chemical change 
causes a redistribution of energy in the system. Thermo- 
chemistry attempts to determine the connection between chem- 
ical changes and the distribution of energy in the changing 
system. 

The state of any chemical system is associated with a cer- 
tain amount of energy, and thermochemistry measures the 
heat developed in the passage to a new state. If we assume 
that the whole of the energy which has been transferred has 
passed into heat, and that none escapes measurement, then the 
amount measured gives the difference of energy betv een the 
first and the second state of the system. It does not, however, 
follow that this is the measure of the chemical energy alone of 
the change. The chemical changes are so associated with the 
physical that it is difficult, if not impossible, to separate them. 

Thermo chemical measurements are made by having the 
reactions occur in a closed chamber immersed in water, so that 
the whole of the heat produced is transferred to the water. 



THERMOCHEMIS TR Y. 203 

The enclosing vessel with its contents constitutes one form of 
calorimeter. 

Principles of Thermochemistry. The heat that is produced 
•or disappears in a chemical change which results in the forma- 
tion of a compound from its elements is called the heat of 
formation of the compound. Compounds in whose formation 
heat is developed are called exothermic compounds; those in 
whose formation heat disappears are called endothermic com- 
pounds. More generally, a reaction associated with the develop- 
ment of heat is exothermic; with the disappearance of heat 
endothermic. 

The thermal changes occurring during the decomposition 
of a compound measure the heat of decomposition of that com- 
pound. The heat of decomposition is numerically equal to 
and has opposite sign to that of formation. The thermal change 
accompanying a chemical change is invariable in quantity. 

The thermo-chemical relations in ordinary reactions are 
usually expressed by enclosing the reacting substances in brack- 
ets, with a comma between, as the first member of an equation, 
in the second member of which is the heat of formation with a 
I or - sign, accordingly as heat is developed or disappears. 
If no sign is given, the + sign is understood. Thus [H 2 0] = 
68360 indicates that 2 grains of H and 16 grains of in com- 
bining evolve 68400 grain-units of heat. [C$ 2 ] = — 19600 means 
that 12 grains of C and 64 grains of S in combining absorb 
19600 grain-units of heat, the latter body being endothermic. 
When a body is separated into its constituents the equation is 
preceded by a — sign: -[H, Cl]= -22000. The brackets are 
sometimes omitted. Then, again, the relations may be indi- 
cated by the ordinary equation followed by a number in the 
second member indicating the thermal result : H 2 -f O = 
H 2 + 68360 ; the decomposition of water H 2 = H 2 + O - 68360. 
In such reactions the symbol aq is used to represent a large 
quantity of water; thus [HC1, aq] = 17320 indicates the heat- 
units produced by the solution of 36.5 grains of gaseous HC1 in 



204 ADDITIONAL GENERAL PRINCIPLES. 

water; again, [H,Cl,aq] =39300 represents the thermal effect of 
the combustion of H and CI in atomic proportions, and the solu- 
tion of the compound in water. These reactions in which water 
is considered may also be written without the brackets, and 
again as follows: 

HCl + aq=HClaq+17320.H + Cl+aq=HClaq+39300. 

The heats of formation of many substances cannot be deter- 
mined directly, because their elements cannot be made to 
combine directly for their formation. It is, however, possible 
to calculate the values in many cases when they cannot be 
directly measured. The underlying principle of such compu- 
tations is that the amount of heat liberated and absorbed during 
a chemical change depends upon the initial and final states of 
the system, and is independent of the intermediate stages. 
Two simple examples illustrating this principle will be given. 

Marsh-gas cannot be formed artificially by the direct union 
of its elements, but its heat of formation may be computed as 
follows: 

C + 2 =C0 2 + 97000; 
2H 2 +0 2 =2H 2 + 136800; 
CH 4 +20 2 = C0 2 + 2H 2 + 212000; 
97000 + 136000 - 212000 = + 21800. 

The heat of formation is thus determined to be 21800. Again, 
(N 2 0) cannot be f ormed directly from its elements, but it sup- 
ports the combustion of carbon, and the heat of this combustion 
is easily found from the reaction 2N 2 + C=C0 2 + 2N 2 + 133900; 
the combustion of carbon gives C + 2 = C0 2 + 97000. The differ- 
ence of these two quantities must be the heat of formation of 
2N 2 0, which is 97000-133900= -36000, or the heat of forma- 
tion of N 2 = —18000; it is therefore an endothermic body. 

The Law of Maximum Work. The widest generalization yet 
made as to thermo-chemical reactions is the law of maximum 
work. The statement of this law has been variously modified 






THERMOCHEMISTRY. 205 

in thermal chemistry, but it was announced by Berthelot, whose 
name it generally bears, in substance as follows : ' ' Every chem- 
ical change accomplished without the intervention of external 
energy tends to the formation of that body or system of bodies 
the production of which is accompanied by the development of 
the maximum quantity of heat." 

Neither this nor any other equally broad statement of the 
law has been substantiated. The most generalized argument 
which discredits this law is that of chemical equilibrium or 
reversible reactions. In these reactions, if one change is exo^ 
thermic the reverse change must be endothermic, yet either can 
be produced at will by varying the proportion of the con- 
stituents. 

Again, there are numerous instances of reactions taking place 
with the absorption of heat, and other possible reactions, under 
the law, which do not take place. Thus, if through a mixture 
of hydrogen, oxygen, and chlorine an electric spark be passed, 
the hydrogen does not combine with the oxygen until all the 
chlorine has entered into combination, though the union of 
hydrogen and oxygen is far more exothermic. 

The efforts to so modify the statement of the law as to make 
the ordinary conditions for many reactions involve foreign 
agencies have not been successful nor increased the utility of 
the law. 

While the statement of maximum work cannot be accepted 
as a law of nature, it does hold true in very many cases; and 
when all the physical conditions of similar chemical processes 
are kept as nearly constant as possible, the processes involving 
the maximum development of heat very generally occur. This 
indicates that the principle of maximum work is likely to be of 
greater significance as more certain conclusions are reached in 
regard to the constitution of chemical compounds and the 
nature of reactions. 

In conclusion it may be stated that thermochemical studies 
have determined series of results each of which expresses many 



206 ADDITIONAL GENERAL PRINCIPLES. 

facts and suggests still others, and as results accumulate they 
will undoubtedly lead to a better understanding of the relation, 
which must exist between chemical composition and chemical 
transformation. The generalizations thus far reached justify 
the attempt to apply them to but few of the considerations to 
which attention is given in this book. 

Chemical Reactions. It will now be evident how imper- 
fectly the ordinary reaction-equation represents even the fairly 
well recognized phenomena involved in the process of chemical 
change. In such equation no indication is given of the energy 
changes; of the influence of mass action, or the relative masses 
of the reagents; nor of the greater or less dissociation of electro- 
lytes in solution. A great many equations indicate reactions 
which are possible only under certain conditions, which condi- 
tions are only partially or not at all represented in the equa- 
tion. The equations give only the initial bodies and the final 
material results, and, except in particular reactions, even these 
are not given in entirety. Besides the unnoted relations above 
referred to there are probably many other minor actions which 
receive no expression in the equation. 

It is proper here to recall attention to the fact that the 
notation commonly used in reaction-equations is inexact in 
view of the conclusions which have been reached as to the 
molecules of elements. In general in the equations there should 
never be indicated single atoms, but always one or more mole- 
cules of an element; thus the expression for the combination of 
oxygen and hydrogen to form water should properly be ex- 
pressed, 

2H 2 + 2 =20H 2 ; similarly, H 2 + C1 2 =2HC1. 

It should be borne in mind that when these reactions are in- 
dicated as containing single atomic symbols, thus, 

H 2 +0=OH 2; H + C1=HC1, 

it is for simplicity and convenience. 



PERIODIC LAW. 207 

The notation and nomenclature of compounds must not 
cause us to forget that the elements do -not exist as such in the 
compound. For instance, the formula HC1 indicates, and we 
say, that hydrochloric acid is composed of H and CI, but it is 
not meant that the elements, as constituents in the compound, 
are the same as in the separate state. The notation indicates the 
simple bodies which in union make the compound ; during union 
the constituents no longer exist as elements. 

Periodic Law — Classification of Elements. This classifica- 
tion is, like other classifications, based upon similarities and re- 
semblances among the bodies put into the same class. Partly 
upon a general similarity of physical and chemical properties, 
the elements have been divided into metallic and non-metallic. 
We have also seen that they may be classed according to their 
valencies. By the first division we have two classes, and by 
the latter eight. 

A third classification has been made which is more funda- 
mental than either of these, and depends upon the atomic 
weights (masses) of the elements. This system of classification 
is known as the periodic system; it is more comprehensive and 
includes the two just named. 

The periodic law upon which the system is based may be 
stated as follows: "The properties of the elements are periodic 
functions of the atomic weights." In less technical language we 
may say that, if the elements be arranged in series in the order 
of their atomic weights, elements with similar properties will 
fall at regular intervals along the series; the properties of the 
consecutive elements will differ, but similar properties will re- 
appear periodically throughout the series. 

It had long been observed that the atomic weights of many 
allied elements have certain simple numerical relations. It had 
been noticed when several members of such groups were arranged 
in order of their atomic weights, that certain atomic weights 
were the arithmetical means of those of the members between 
which they fell. 



208 



ADDITIOXAL GENERAL PRINCIPLES. 



This is illustrated by the elements and their atomic weights 
given below: 



Elements. 


Weight. | Mean of! and 3. 


1. Li 

2. Na 

3. K 


23 


7 + 39-2 = 
23 


39 




1. K 

9 Rb 


39 

85 3 . 


39 + 132.6-^-2 = 
85.8 


3. Cs 


132.6 




1. P 31 i 31-120-2 = 

2. As 75 ! 75.5 

3. Sb 120 



By arranging the members of different allied groups in order 
of their atomic weights it will be seen that the variation in 
atomic weights in each group is very nearly the same, and 
nearly three times that between the first and second group; 
this is shown bv the following table : 



Atomic 


Consecutive 


Atomic 


Consecutive 


Atomic 


Consecutive 


Weight. 


Differences 


V eight. 


Differences. 


Weight 


Differences. 


0= 16. 




Xa= 23. 




Mg= 24. 






16. 




16. 




16. 


S= 32. 




K = 3*9. 




Ca= 40. 






47. 




46.3 




47.4 


Se = 79. 




Rb= 85.3 




Sr = 87.4 






46. 




47.3 





49.5 


Te=125. 




Cs = 132 6 




Ba=136 9 





Such facts as these satisfied chemists that the properties of 
the elements were in some way related to their atomic weights. 
Newlands first pointed out, 1864-66, the fact that the elements 
when arranged in the order of atomic weights exhibited a 
periodic recurrence of properties. Shortly afterwards the law 
was elaborated and developed by Mendeleefi . whose name it 
generally bears. About the same time, important extensions 
of it were made by Meyer. 



PERIODIC LAW. 



209 



That the chemical properties are in harmony with the periodic 
system may be best seen by arranging in order of increasing 
atomic weights the first fourteen elements which follow after 
hydrogen. This arrangement is shown in the table below, to- 
gether with some of the corresponding compounds of the ele- 
ments : 





1 


2 


3 


4 


5 


6 


7 


1st series 
2d series 


Li = 7. 
Na = 23. 


Be= 9. 
Mg = 24. 


B =10.9 
Al = 27. 


C = 12. 

Si = 28. 


N = 14. 
P = 31. 


= 16. 
8 = 32. ' 


F= 19. 
Cl = 35.5 


Chlorides 


J LiCl 
INaCl 
Li 2 
Na 2 


BeCl 2 

MgCl 2 

(Be 2 2 )BeO 

(Mg 2 2 )MgO 


BC1 3 

(A1C1 3 ) 2 

B 2 3 

AI2O3 


CC1 4> CH 4 
SiCl 4 ,SiH 4 
(C 2 4 )C0 2 
(Si20 4 )Si0 2 


NH 3 
PH 3 

P2O5 


OH 2 
SH 2 

(S 2 b 6 )so 3 


FH 

C1H 

ci 2 b 7 



In the first series each member of the series has certain 
characteristic properties and there is a gradation of properties. 
In the second series similar properties and gradations appear. 
Passing from column 4 to the left, in both series the members 
become more electro-positive or distinctively metallic, while to 
the right of column 4 they grow more distinctively non-metallic. 
The two members in each column also show striking resem- 
blances; thus lithium resembles sodium, carbon resembles 
silicon, and fluorine resembles chlorine, etc. 

Taking their valencies as shown by their hydrogen and 
chlorine compounds it will be seen that they are the same in 
both series, the valencies by this test increasing to the center, 
and then decreasing. Comparing their compounds of oxygon, a 
different result is reached : the valencies increase in both series 
from left to right. The highest oxide is taken in each case where 
there are more than one, and to better express the gradation, 
the formulae of the oxides are so written as to indicate the pro- 
portions of oxygen combined with two atoms of each element. 
It is thus seen that after we pass over seven elements of the 
fourteen, the properties exhibited by them are repeated in the 
next seven. The number of elements passed over before a re- 
currence of similar properties is termed a period. It is well to 



210 ADDITIONAL GENERAL PRINCIPLES 

remark here that not only the properties of the elements recur ,. 
but also the properties of the compounds formed. 

With the fourteen elements above given the reappearance of 
properties is found with the eighth element, so that there are 
two periods of seven elements in this series. These two periods 
are termed short periods, for reasons which will now appear. 

If the tabulation of the elements in order of atomic weights 
be continued beyond the fourteen above given, it is found that 
seventeen elements are passed over before there is a distinct 
return to the properties displayed by the first members of the 
short periods. This series of seventeen elements, terminating 
with bromine, constitutes what is called a long period. Con- 
tinuing in the order of increasing atomic weights, another long 
period occurs, terminating with iodine. Each element of the 
short series has a corresponding representative in the first con- 
secutive seven of these two long periods, with one exception — 
the seventh term of the second long series is missing. In each 
of these two long periods, the first and last seven members show 
similarities in many important chemical characters, while the 
three middle members (8, 9, and 10) of the period form a sepa- 
rate group and are called transitional elements. This is equiva- 
lent to saying that the properties of the short periods reappear 
twice in the long periods, once in the first seven and once in the 
last seven, the transitional elements being intermediate. 

The other elements after iodine appear to fall into three 
similar long periods, but in these periods there are many gaps, 
and with few exceptions the known representatives are rare 
elements. 

By arranging the elements so that the first and last seven 
members of the long periods fall into column with the corre- 
sponding members of the short periods, the transitional ele- 
ments (8, 9, and 10 of the long periods) being in separate col- 
umns, we get the following table, which is one of the groupings- 
arranged by Mendeleeff: 



PERIODIC LAW. 



211 



Group. 


1 


2 


3 


4 


5 


6 


7 


8 




Series . 
1 


A B 

H~ 
Li 

Na 
K 

Cu 
Rb 

Ag 
Cs 

Au 


A B 


A B 


A B 


A B 


A B 


A B 


Fe, Co, Ni 
Ru, Rh, Pd 




2 
3 

4 
5 
6 

7 
8 


Be 

Mg 

Ca 

Zn 
Sr 

Cd 
Ba 

Hg 


B 

Al 
Sc 

Ga 
Y 

In 
La 

Y 

Tl 


C 

Si 
Ti 

Ge 
Zr 

Sn 
Ce 

Pb 

Tk 


N 

P 
V 

As 
Nb 

Sb 
Di 

Ta 

Bi 




S 
Cr 

Se 
Mo 

Te 

W 
U 


F 

CI 
Mn 

Br 

I 




9 
10 
11 

12 


Os, Ir, Pt. 






R 2 


(RO) 
R 2 2 


R2O3 


R 2 4 


(R0 3 ) 
R 2 5 


R 2 6 


R 2 7 




Typical 
oxides 










RH 4 


RH 3 


RH 2 


RH 

















In this arrangement the elements fall into eight groups in- 
dicated by the vertical columns from one to eight, the eighth 
group containing the transitional elements. These groups are 
the natural families of the elements and contain those which 
are most closely allied in properties. The horizontal columns 
contain the series, of which there are twelve. The second 
series begins with lithium, so that the first series contains only 
hydrogen. The elements of the same group which fall in the 
even series resemble each other more nearly than they do those 
of that group which fall in the odd series; this is also true of 
elements in the same group in odd series. Thus calcium is less 
like zinc than it is like strontium; potassium is less like copper 
than it is like rubidium; while zinc is more like magnesium 
than it is like copper. Thus closer similarity between alternate 
members of the same group permits a separation of each group 
into sub-groups, as indicated by the brackets in each group 
column. This alternation shows that the periodic return of 
properties to the same value is more perfect after passing over 
two series, or that each period is composed of two series; this 
fact has been previously noted as regards all elements after the 
two typical short periods, terminating with chlorine. 

In the last two horizontal columns of the table are given 



212 ADDITIONAL GENERAL PRINCIPLES. 

the general formula of some of the compounds of the different 
elements. a R" represents one atom of any element of a group, 
and the oxides selected are those common to all the elements of 
a group. These two columns show admirably both the simi- 
larity in elements of the same group and the recurrence of prop- 
erties in the series. 

The periodic law is also illustrated in the recurrence of phys- 
ical properties, such as malleability, ductility, melting-point, 
electrical properties, and specific gravities. The atomic volume 
or the quotient of the atomic weight by the specific gravity may 
well be chosen to show the general conformity to the periodic 
law. The atomic volume decreases to the middle element of the 
short periods and then increases to the last one. A similar de- 
crease and increase in the atomic volumes takes place in the 
next three long periods, the recurrence being reached in the 
transitional elements at the end of the series. 

Application of the Periodic Relation. The periodic law has 
been of service in deciding the atomic weights of some elements, 
and it has enabled the chemist whose name it bears (Mendeleeff) 
to foretell with accuracy the existence and properties of ele- 
ments which have been subsequently discovered. The law un- 
doubtedly gives the most scientific classification of the ele- 
ments, and investigation thus far confirms the assumption that 
it is a fundamental law of chemistry. It promises to furnish a 
new basis for physical investigation as well as for classification 
of elements and compounds. No satisfactory theory has been 
offered in exp'anation of the law. 

RADIOACTIVE ELEMENTS. 

Becquerel in 1898 first discovered that the compounds of 
uranium emitted peculiar radiations which were capable of 
acting upon a photographic plate screened from light, and 
when these radiations were passed through atmospheric air or 
other gas it caused it to become a conductor of electricity; 



RADIOACTIVE ELEMENTS. 213 

the gas in such condition is then said to be ionized. Shortly 
after the discovery of Becquerel it was noticed by M. and Mme. 
Curie that certain uranium ores were more active in giving off 
rays than pure uranium. By concentrating the residues from 
a large quantity of the ore from which the uranium had been 
extracted, they separated a product which was more than a 
million times as active as uranium. The activity was later 
found by them to be due to very small quantities of three sub- 
stances previously unknown: radium, actinium, and polonium. 

Of the three new bodies present in the uranium residues, the 
properties of radium have been most fully studied, and the 
following remarks apply to this substance unless otherwise in- 
dicated. Radium has not been isolated; its properties are in- 
vestigated mainly through the study of its chloride and bromide. 
Its spectrum allies it to the alkaline earths, and its chemical 
behavior is analogous to barium; it was only by a most labo- 
rious process that its chloride was freed from that of barium. 
The radioactive bodies were present in the original ore, pitch- 
blende, in exceedingly small quantities, less than one millionth 
o ' one per cent. M. and Mme. Curie followed the concentration 
of the new bodies in their chemical operations by determining 
the radioactivity of the residue after each operation. This was 
done by measuring the electric conducting power of a layer of 
air exposed to the rays emitted from each succeeding product. 
The detection of the presence of a radioactive element by its 
effect on the conducting power of a gas is many thousand times 
more sensitive than by spectroscopic observation; but for this 
delicate method the discoveries made relating to the radio- 
active bodies would have been quite impossible. The atomic 
weight of radium is 225. 

Properties of Radium Salts. Radium salts are self-luminous; 
the rays from them affect a photographic plate from which light 
is excluded, and produce phosphorescence in a large number of 
bodies, as the diamond, ruby, fluor-spar, and many others. 
The action of the rays increases greatly the electric conducting 



214 ADDITIONAL GENERAL PRINCIPLES 

power of gases and, to a certain extent, that of both liquid and 
solid dielectrics. The rays produce chemical effects, converting 
oxygen into ozone, and change the color of certain salts, eA^en 
producing a color effect in certain glass; they are also capable 
of producing burns or wounds which are both painful and tedi- 
ous in healing; they produce paralysis in mice and caterpillars. 

Kinds of Rays. From radium salts there are emitted at 
least three kinds of rays, designated as a (alpha), /? (beta), and 
y (gamma). The a rays have small penetrating power, are 
absorbed by thin layers of matter, and only slightly deflected 
in a strong magnetic field. They are very active in ionizing a 
gas, making it an electric conductor; their action in this respect 
is a hundredfold that of the .3 and j rays combined. They pro- 
duce phosphorescence in certain substances and only slightly 
affect a photographic plate. The a rays are given off by all 
radioactive bodies. The a particle whose motion constitutes 
the ray has a mass approximately twice that of the hydrogen 
atom and moves with a velocity about one tenth that of light : 
the particle bears a positive charge of electricity. 

The .? rays are strongly deflected in a magnetic field; they 
have greater penetrating power than a rays, but only a slight* 
power to ionize a gas or affect a photographic plate; their 
phosphorescent action is less than that of the a particles. The 
velocity of the ,3 particles approximates to that of light and 
their mass is about ^ that of the hydrogen atom. The p 
rays are given off from all radioactive substances except 
polonium. The y rays differ from the a and t 3 rays in that they 
involve no translation of particles, but appear to be non-periodic 
pulses in the ether, similar in many respects to X or Roentgen 
rays and akin in some respects to short waves of light. The 
y rays are present wherever /3 rays are given off. The pene- 
trating power of j rays is very great, being sufficient to pass 
through a foot of iron or several inches of lead; they cannot be 
deflected by a magnet; they are the chief agent in the physi- 
ological and photographic action of radium salts. 



RADIOACTIVE ELEMENTS 215 

Heat from Radium Salts. In addition to the above proper- 
ties of radium salts there is another still more extraordinary to 
note, viz., their spontaneous and continuous evolution of heat. 
Salts of radium have a temperature that is continually above 
that of the surrounding medium. It is found that radium gives 
off heat enough to melt its own weight of ice every hour. This 
expenditure of energy goes on apparently without diminution 
for, at least, considerable periods of time. This is a most inter- 
esting and startling discovery and shows that the source of the 
energy is almost imperceptibly deflated. 

Emanations from Radioactive Bodies. In addition to the 
a, /?, and y rays and the large quantity of heat given out by 
radium, this element and certain of the other radioactive 
bodies give off an emanation. The emanation from radium in 
many of its properties resembles the chemically inert gases of 
the argon group. By heating or by dissolving radium salts in 
water the emanation is given off and may be collected like any 
other gas. Its molecular weight appears to be about 100. It 
condenses at about —152° C. The radioactive salts when 
heated lose their emanating power, but they regain it in time. 
The emanation itself gives off a rays, ionizing gases, and it is 
found that nearly three fourths of the heat evolved from radium 
salts proceeds from the emanation present in them. The 
emanation does not emit the /? and y rays. The activity of the 
emanations both from thorium and radium decays rapidly with 
time, the former falling to half its initial value in one minute, 
and the latter the same amount in 3.7 days. 

Helium Produced from Radium. In addition to the re- 
markable properties of radium and its emanation already given, 
it further appears that the emanation undergoes still other 
changes, ultimately yielding as many as five or six products, 
each product being the offspring of the preceding and the parent 
of the succeeding. Somewhere in this chain helium appears 
as one of the products. It has been shown that helium is not 
present in the foremost links of the chain, but is a result of the 



216 ADDITIOXAL GENERAL PRINCIPLES, 

changes taking place. We thus have the first instance of one 
element being developed from another. Helium is the lightest 
substance except hydrogen, has an atomic weight of 4, is not 
radioactive, and has not been liquefied; the emanation from 
which it is derived has a molecular weight of 100, is radio- 
active, and liquefies at —152° C. 

Properties of Radioactive Bodies and Other Ionization. 
The more important and extraordinary properties of radium 
and its emanations have now been stated, and while radium 
alone has generally been referred to, the same or similar re- 
markable properties are exhibited by several other bodies, which 
fact places them among the radioactive substances. The other 
substances in which radioactivity is found to exist to a con- 
siderable extent are barium, thorium, and actinium; polonium, 
detected by the Curies, was found not to be a single substance. 
It is not practicable to describe here the individual properties 
of each substance, but there is a certain action common to them 
all which can also be brought about independently of the pres- 
ence of any of these bodies: this is the ionizing action on 
gases, rendering them conductors of electricity. This ioniza- 
tion of a gas can be effected in several other ways : (1) by a high 
temperature; (2) by bringing the gas into contact with an in- 
candescent metal or carbon; (3) by the passage of the electric 
discharge through high vacua with production of cathode rays; 
(4) by the action of violet light, and by still other means. The 
gas thus ionized is found to be permeated with charged particles, 
some positive and others negative; these particles are caHed 
ions, and the process ionization. The negatively charged par- 
ticles have been named corpuscles, also electrons. These cor- 
puscles are then particles which are brought into existence by 
one of the several ways stated : they pass from the heated metal 
or other source, bearing negative charges of electricity and 
moving with certain velocities. The charge, velocity, and mass 
of the corpuscles from certain sources have been determined. 
The mass of the negative ion or corpuscle is always the same 



RADIOACTIVE ELEMENTS. 217 

no matter what gas is ionized, nor what the ionizing agent. 
This mass is about —■ that of the hydrogen atom; they carry 
the same electric charge as the hydrogen ion in electrolysis; 
their velocities vary from about ^ to \ that of light, depending 
upon the intensity of the electric field. The cathode rays, the 
rays which proceed from the cathode plate during electric dis- 
charge in high vacua are a beam of corpuscles. These cathode 
rays by impinging on the glass of the vacuum tube or a metal 
target therein give rise to the X or Roentgen rays. The mass 
of the positive ion of a conducting gas is not the same for all 
gases; this mass is of the same order of magnitude as the cor- 
responding ion in electrolysis it carries the same quantity of 
charge as the corpuscle, and moves with a much smaller velocity. 

Relation between Radioactive Rays and the Ions of Gases. 
The /? rays or particles from radioactive bodies have been 
shown to be practically identical with the negatively charged 
particles or cathode rays of rarefied gases, except that the /? 
particles move with greater velocity, their velocity approaching 
that of light; their mass is the same as the cathode particles, 
being about T -^ F that of the hydrogen atom; the kind and 
amount of charge of the /? particle is the same as for that of the 
cathode particle. 

The alpha particles or rays bear positive charges, as do the 
positive gaseous ions; but while the mass of the positive ion 
varies with the different gases, the mass of the alpha particles 
is approximately twice that of the hydrogen atom. 

The y rays which are always present with /? rays in radio- 
action are believed to be a form of X ray ; this latter, it will be 
remembered, is always produced by the cathode ray, which, as 
just stated, is identical with the /? ray. We thus reach the 
conclusion that radioactive bodies emit particles which have 
only about 770 the mass of the hydrogen atom, and a similar 
small mass appears as corpuscles or negative ions in ionized 
gases, the mass being the same no matter what the nature of 
the gas or the source of the ionization. 



218 ADDITIONAL GENERAL PRINCIPLES. 

Conclusions. The phenomena of radio activity and allied 
actions lead to the conclusion that particles having only about 
77 4 the mass of the hydrogen atom are separated from certain 
forms of matter, and that the smallest masses are the same 
whatever their sources; that certain elements are capable of 
spontaneous decomposition, and that one element, at least, by 
such decomposition has produced another, as when helium 
results from the radium. This natural transformation, however, 
should not be taken for nor confounded with the artificial 
transmutation of one element into another. Radioactive phe- 
nomena are shown to be atomic and not molecular, by the 
fact that the activity of radium, for instance, depends upon the 
amount of radium present and not upon the amount of the 
salt that may contain it. The process of change in the radio- 
elements are conclusively shown to be entirely different from 
any previously observed in chemistry, by the one fact that it 
has been found impossible to alter by artificial means the rate 
or nature of change that is taking place spontaneously. Tem- 
perature, which is usually such an important factor in affecting 
the rate of ordinary chemical action, such interaction as we 
recognize to be molecular, is in these cases almost entirely 
without influence. The radioactive changes proceed at the 
same rate at the temperature of red heat and at that of liquefied 
air, -190° C. 

Artificial effort applied over the widest range of temperature 
has not up to this time been able to affect the stability of the 
elements, that is, decompose the accepted atoms. This fact 
shows that atomic stability is independent of the highest arti- 
ficial temperatures. The fact that thfs natural, spontaneous 
decomposition proceeds independently of the temperature is 
also a negative indication that the action is an atomic one. 

It now seems most probable that the radioactive processes 
which result in a chain of distinct products are due to the spon- 
taneous disintegration of the atoms of these bodies, each disin- 
tegrating atom passing through a succession of definite changes 



RADIOACTIVE ELEMENTS. 219 

generally accompanied by the emission of rays. The new and 
characteristic forms of matter that thus successively result are 
not products of transmutation, but transformations resulting 
generally from material loss or gain. This theory involves the 
conception that the atoms themselves are complex systems and 
only maintain their integrity so long as the system remains in 
stable equilibrium. The energy developed from radium, for 
instance, is not derived from any extraneous source, but is con- 
tained in the radium atom and is developed by the impinging 
of the alpha particles upon substances as they escape from the 
atom. To be endowed with such energy the units of the atomic 
systems must have high velocities before they break away from 
equilibrium and depart from their accustomed orbits. This 
disintegration of radium takes place at such rate that about one 
half any given quantity of radium would disintegrate in 2600 
years, half the remainder in the next 2600 years, and so on. 

The study of the radioactive bodies has shown that certain 
of the chemical elements, at least, seem to be subject to the 
ravages of time and through their disintegration produce others 
equally entitled to be classed as elements. This disintegration 
involves the separation and has resulted in the detection of 
masses far smaller than the hydrogen atom, and these small 
masses seem to have identical properties from whatever element 
derived; this disintegration also reveals the latent possibilities 
of almost fabulous amounts of energy, accumulated at the be- 
ginning in complex atomic systems. The systems in certain 
cases are likely to go to pieces,* but the radioactive processes 
are spontaneous and as yet can neither be delayed, hastened, 
nor controlled. The three heaviest metals, uranium, thorium, 
and radium, are those thus far found to display this self -destruc- 
tive tendency to the greatest degree. Helium has been shown 
to result from radium, and at present radium seems to be the 
offspring of uranium, though not resulting directly from it. 
The final product of the disintegration of radium has not been 
definitely determined, but the indications arc that it may be 



220 ADDITIONAL GENERAL PRINCIPLES. 

proved to be lead. The permanence, stability, and importance 
of our chemical units, those constant masses which react in all 
chemical changes that can be produced or influenced by arti- 
ficial means — the atomic weights of chemistry — under the proper 
conception of their individuality have not been disturbed by the 
radioactive developments. 



CHAPTER IV. 

CHEMISTRY OF THE METALS AND THEIR 
COMPOUNDS. 

THE ALKALI METALS. 

The most important elements of this group are sodium 
and potassium. The other members are lithium, rubidium, 
and caesium. The first two are abundant in nature and 
widely distributed. Lithium is widely distributed, but 
only in small quantity. The last two members of the group 
are still more rare. These elements are highly electro-posi- 
tive and, as already stated, their hydroxides are power- 
fully alkaline and their salts are generally soluble. The 
elements are soft, silvery- white metals, all of which decom- 
pose water, and the last two of the group take fire in the 
air. 

POTASSIUM; K' ; 38.9. 

Occurrence. Potassium is not found in a pure state in 
nature, but it occurs abundantly as a chloride in combina 
tion with other chlorides, forming immense deposits. In 
combination with silica and alumina it is a common con- 
stituent of the igneous and metamorphic rocks. From t hese 
rocks, by disintegration, its salts pass into the soil and 
finally into plants, of which they are essential food ingre- 
dients. 

From plants the salts of potassium pass into the organ- 
isms of animals. In plants potassium is mainly present as 

salts of vegetable acids. 

221 



222 IXORGAXIC CIIEjIISTRY. 

Preparation. Potassium was first isolated by Davy in 
1807, by decomposing the hydroxide by electricity, the 
potassium appearing at the negative pole. 

The method of Davy was not then practicable on a com- 
mercial scale. Until recently potassium has been prepared 
by deoxidizing potassium carbonate with charcoal. For a 
good yield the ingredients should be thoroughly mixed. 
An intimate mixture of potassium carbonate and charcoal 
is obtained by calcining potassium tartrate (C 4 H 5 6 K) in a 
covered crucible, and this method is generally followed in 
preparing the carbonate for deoxidation. 

The mixture of potassium carbonate and carbon is dis- 
tilled in an iron retort from which a short iron pipe leads to 
a receiver containing petroleum and which is kept cool by 
ice-water. YVnen the retort is heated to a high tempera- 
ture the potassium distils over and condenses under the 
petroleum. The reaction occurring is indicated by the fol- 
lowing equation: 

K 2 C0 3 + C 2 = K a + 3CO. 

The metal thus obtained is not pure and has to be redis- 
tilled or subjected to other treatment to perfectly purify it. 
Recently the metal has been obtained by deoxidizing 
the hydroxide by carbon: 

3KOH + C = K 2 C0 3 + H 3 + K. 

In Castner s method a mixture of iron and carbon is made 
by heating together tar and haematite iron ore; this mix- 
ture is sometimes called iron carbide, and is used in the 
process instead of charcoal alone. The action of the iron 
is mainly mechanical, serving to keep the carbon in con- 
tact with the fused hydroxide. 

Metallic sodium is now manufactured by the electrolysis 
of sodium hydroxide, and the same process would undoubt- 
edly be applied to the production of potassium if the sodium 



METALLIC ELEMENTS. 223 

made did not fully supply at lower cost the industrial de- 
mands for an alkaline metal. 

Properties and Uses. Potassium is a silver- white metal, 
specific gravity of .865 ; it rapidly tarnishes when exposed 
to the air. It floats on water, and takes fire when placed 
upon water or even upon ice. More properly speaking the 
potassium decomposes the water, and the liberated hydro- 
gen takes fire, at the same time volatilizing some of the 
potassium, which burns with a violet color. Potassium 
melts below the boiling-point of water. The greater diffi- 
culty attending the preparation of potassium, and the fact 
that sodium can replace it in industrial operations, have? 
almost entirely limited its application to laboratory pur- 
poses. It will be seen from the relative atomic weights of 
potassium and sodium that, for equal weights, the latter 
element can do more chemical work. 

Potassium Carbonate ; K 2 C0 3 . This important salt is ob- 
tained on a commercial scale by several different processes. 
Formerly most of the potash or crude carbonate was ob- 
tained from wood-ashes, but this source has greatly decreased 
in importance and now only parts of the United States, 
Canada, Russia, Hungary, and Gralicia supply it from this 
source. The amount of the carbonate, however, from wood- 
ashes is greater than that from any other single source. 

Potassium Carbonate from Wood-ashes. It has already 
been stated that potassium exists in plants as the salts 
of vegetable acids. When the wood is incinerated, these 
salts are decomposed and the potassium is left in the form 
of the carbonate. Of course the ashes contain other mineral 
substances resulting from other salts present in the plants. 
By lixiviation with water the more soluble salts are separa- 
ted from the less soluble ; the former consists mainly of 
potassium carbonate with considerable portions o( potas- 
sium sulphate and chloride. By evaporation a considerable 
portion of the sulphate may be removed, as it is less soluble 



224 INORGANIC CHEMISTRY. 

than the carbonate and crystallizes first. The residue then 
evaporated to dryness and calcined gives the crnde potash 
of commerce, which contains much potassium chloride and 
some sulphate. When greater care is observed in the 
process the product is purer and known under the name 
of pearlash. 

Potassium Carbonate from Beet-root Molasses. In 
making sugar from the beet-root there is left a syrup which 
cannot be made to crystallize ; this syrup is rich in mineral 
salts, especially those of potassium. The syrup is first 
fermented for the production of alcohol. The liquor left 
behind is called "vinasse" in France, and " schlempe" 
in Germany. This liquor evaporated to dryness, calcined, 
and the cinder lixiviated furnishes a high percentage of 
potash salts, K 2 C0 3 , K 2 S0 4 , and KC1. This industry has 
obtained great development in Germany and France. 

Potassium Carbonate from the Chloride. A large 
amount of potassium carbonate is made from the native 
chloride by a process similar to that employed in the manu- 
facture of sodium carbonate from common salt, yet to be 
described. ■ 

Potassium Carbonate from Sheep' s-wool. The washings 
from sheep' s-wool are called suint and contain a con- 
siderable quantity of potassium, mainly combined with 
animal acids. By evaporating the liquid to dryness and 
burning the residue, the organic salts are decomposed and 
the carbonate of potassium left. This is separated by lix- 
iviation from the ash. 

The potassium carbonate is obtained from other sources 
in small quantity, but not on a commercial scale. 

Properties and Uses of Potassium Carbonate. The normal 
potassium carbonate is a white solid, extremely deliques- 
cent, and soluble in less than its own weight of water, yield- 
ing a strongly alkaline solution. It is insoluble in alcohol. 
This substance is an important compound, being used in the 



METALLIC ELEMENTS. 225 

manufacture of soap and glass. In many States of America 
the country population make their own soap, obtaining the 
potash from the ashes of the wood used as fuel. 

The Acid Carbonate or Bicarbonate of Potassium. It can be 
prepared by passing carbon dioxide through moist potas- 
sium carbonate or through a solution of potassium car- 
bonate. The salt is less soluble and less alkaline than the 
normal salt. 

It is converted into the normal carbonate by heat : 

2KHC0 3 (heated) = K 2 C0 3 + H 2 + C0 2 . 

It is used to a small extent in medicine. 

Potassium Hydroxide ; KOH. This substance may be pre- 
pared by adding a solution of slaked lime to a boiling 
dilute solution of potassium carbonate : 

K 2 C0 3 + Ca(OH) 2 = CaCO s + 2KOH. 

The reaction will not take place if the solution of the car- 
bonate be too strong. The solution decanted from the 
insoluble calcium carbonate and evaporated, leaves a clear 
oily liquid which solidifies to a clear white mass on cooling. 
It is often fused and cast into slabs or sticks. 

The hydroxide is a white solid which can be melted and 
volatilized, but is not decomposable by heat. It is deliques- 
cent and readily absorbs carbon dioxide, forming the car- 
bonate, and is frequently used for removing carbon dioxide 
from gases. It is very soluble in water and evolves much 
heat in dissolving ; is strongly alkaline, being the most 
powerful alkali in general use. It softens and destroys the 
skin, and on this account is used as a cautery. It is one of 
the most useful agents in the laboratory. Near Stassfurth 
in Germany, caustic potassa is now produced in large quan- 
tity by decomposing a solution of potassium chloride by 
electricity. The works are primarily for the production of 
chlorine, and the hydroxide is a valuable by-product 



225 INORGANIC CHEMISTRY 

The hydroxide is prepared by electrolysis at several other 
places. It is commercially used in the manufacture of soft 
soap. 

Potassium Chloride ; KC1. This salt is now almost exclu- 
sively obtained from the mineral carnallite, which is a 
double chloride of potassium and magnesium, KCl,MgCl a , 
6ELO. Carnallite is found in vast quantities overlying the 
Stassfurth salt beds. The chloride is an important raw 
material for manufacturing potassium, the carbonate, the 
nitrate, and as a source of chlorine. 

Potassium Iodide and Potassium Bromide: EI and KBr. These 
compounds are used to a considerable extent in photography, in medicine, 
and in the laboratory. 

They are formed in the same way. by passing iodine or bromine into a 
solution of potassium hydroxide. 

Nitre; Saltpetre; KN0 3 . This important salt is often 
found as an efflorescence upon the surface of the soil in hot 
dry climates. It results from the oxidation of nitrogenous 
organic matter in the presence of potash in the soil. The 
formation of nitre under these circumstances is due to the 
presence of specific microbes, and the nitrification does not 
take place without them. Nearly all of the native saltpetre 
in commerce comes from the East Indies, one of the districts 
of Bengal supplying the greater portion. It is chiefly 
found in the neighborhood of villages, where the animal 
refuse supplies an abundance of organic nitrogen. The sur- 
face of the soil which shows the white efflorescence is 
scraped off and lixiviated with water. This solution evap- 
orated to crystallization furnishes crude nitre, in which 
form it comes into market. 

This native process has been imitated artificially in the 
nitre beds or saltpetre plantations. In Sweden formerly 
every landowner was obliged to furnish the government 
with a certain quantity of nitre. In France during the 



METALLIC ELEMENTS. 227 

Revolution the artificial production of nitre was compul- 
sory. 

In the artificial process animal and vegetable refuse of various kinds is 
mixed with wood-ashes, calcareous earthy material, old mortar, bones, etc. 
This mass is occasionally moistened with stable drainings. After the lapse 
of the proper time, watering is discontinued and salts soon effloresce on the 
surface of the heap. The surface layer to the depth of a few inches is then 
removed and the soluble salts dissolved out. The nitrates found in the 
solution are those of potassium, calcium, magnesium, and ammonium; the 
last three of which may be transformed into potassium nitrate by the 
addition of potassium carbonate to the solution. 

The demands of the Crimean War (1853-56) proved for 
the first time that these sources of supply were insufficient 
and the process of manufacture from sodium nitrate, Chili 
saltpetre, was introduced. 

Nitre from Chili Saltpetre. By far the greater portion 
of the nitre which now comes into the market is made 
from sodium nitrate, NaN0 3 , by treatment with potassium 
chloride. Double decomposition ensues in accordance with 
the equation 

JSTaN0 3 + KC1 = NaCl + KJTO 3 

The reaction is accomplished by mixing at boiling tempera- 
ture equivalent quantities of strong solutions of the two 
salts. In accordance with the law of insolubility the least 
soluble salt at the boiling temperature (NaCl) is formed and 
precipitated. The crystallized sodium chloride is removed 
from the hot solution and the liquid allowed to cool; during 
the cooling the salt least soluble in cold water crystallizes 
out (KN0 3 ). The solubility of the sodium chloride is 
about the same at boiling and common temperatures, so 
that there is no additional separation of it by cooling, while 
the solubility of the potassium nitrate is decreased more 
than six times by the reduction of temperature. 

Properties of Potassium Nitrate. Potassium nitrate crys- 
tallizes in six-sided rhombic prisms surmounted by six- 



228 INORGANIC CHEMISTRY. 

sided pyramids. It lias a cooling and slightly bitter, saline 
taste. Heated above its f using-point it evolves oxygen and 
is reduced to the nitrite ; at a still higher temperature the 
nitrite is decomposed with evolution of nitrogen and 
oxygen, leaving the oxide of the metal. 

The salt is soluble in less than four times its weight of 
water at 18° C, the solubility increasing very rapidly with 
the temperature ; at 100° C. water dissolves nearly two and 
one half times its weight of the salt. 

Potassium nitrate, like the nitrates generally, is a 
powerful oxidizing agent. Its formula shows it to contain 
very nearly one half of its weight of oxygen, five sixths of 
which are available for the oxidation of the combustible 
body. It is chiefly used in the manufacture of black pow- 
der and in pyrotechny. 

Potassium Chlorate; KC10 3 . This salt is a white crystal- 
line solid and like the nitrate is an oxidizing agent. It parts 
with its oxygen more readily than does the nitrate. At a 
high temperature it acts violently upon combustible bodies. 
If a jet of hydrogen or coal gas be played upon the melted 
salt, ignition ensues and the gas burns brilliantly. The 
chlorate is much used in pyrotechny. 

The common friction primers for firing cannon contain 
a mixture of the chlorate, sulphur, and antimony sulphide 
made into a paste with dissolved shellac. A pull on the 
lanyard withdraws a little rasp inserted in the primer and 
thus explodes the mixture, which ignites the powder in the 
lower part of the tube, and this communicates the flame to 
the charge in the gun. The fact that a mixture of it and 
; sulphur explodes by friction prevents its use in the manu- 
facture of black powder. Its use as an oxidizing agent in 
^matches has already been referred to. By heat it is even- 
tually decomposed into potassium chloride and oxygen : 

2KC10 3 (heated) = KC1 + KC10 4 + O,; KC10 4 = KC1 + 4 . 



METALLIC ELEMENTS. 229 

For this reason it is the most convenient source for obtain- 
ing oxygen in the laboratory, as has already been stated. 
The chlorate may be prepared by the action of chlorine 
upon the hydroxide. It is now almost exclusively manu- 
factured by the electrolysis of potassium chloride, which 
process first yields the hydroxide and chlorine. 

Potassium Sulphates. The normal sulphate occurs native, associated 
with the sulphate and chloride of magnesium in the mineral Tcainit, from 
which it may be readily separated. It is also produced as a by-product 
in several industrial operations. Kainit is used as a fertilizer, and potas- 
sium sulphate is used in the manufacture of alum. The formula for kainit 
is K 2 S0 4 ,MgS0 4 ,MgCl 2 Aq. The bisulphate, KHS0 4 , can be prepared by 
the action of sulphuric acid upon nitre. 

OTHER COMPOUNDS OF POTASSIUM. 

Oxides of Potassium. There are several oxides of potassium, the best 
known of which is K 2 4 . This is the final product of the combustion of 
potassium in air or in oxygen. K 2 is thought to result when KaO* is 
heated to a high temperature or when the hydroxide and potassium are 
heated together. The evidence of the existence of this oxide is deemed by 
some good authorities as unsatisfactory. 

Potassium forms sulphides whose formulae are K 2 S, K 2 S 2 , K 2 S<, K 2 S 6 , 
and K 2 S 7 . The compound KHS also exists. 

SODIUM; Na'; 22.9. 

Sodium does not occur in a free state in nature. The 
most abundant natural compound of it is the chloride or 
common salt. Sodium, like potassium, in combination 
with silica and alumina, is a common constituent of certain 
feldspars which go to make up many igneous and metamor- 
phic rocks ; it is not, however, so frequently present in the 
rocks as potassium. Sodium also occurs abundantly in the 
native sodium nitrate. 

The discovery of potassium naturally led Davy to the 
discovery of sodium, which he also isolated in 180? by a 
process entirely similar to that by which he obtained 
potassium. 



230 IXORGAXIC CHEMISTRY. 

Until 1886 sodium was manufactured in a manner simi- 
lar to that described for potassium, namely, by reducing 
the carbonate with charcoal: 

Xa,CO s — 2C = Na, — 3CO. 






In 1886 the above process was superseded by that of 
Castner, which consists in the deoxidation of the hydroxide 
by carbon, as indicated by the equation 

3NaOH + C = Xa 2 CO s — H 3 + Na. 

Sodium is now mainly prepared by Castner' s electro- 
lytic process, which consists in electrolyzing fused caustic 
soda. Sodium and hydrogen appear at the cathode and 
oxygen at the anode. The sodium ascends through the 
liquid and is collected in an iron pot inverted over the 
cathode, the hydrogen escaping. Since about 1895 nearly 
all the metal has been thus obtained. It is thus largely 
produced at Xiagara Falls. 

Properties and Uses. Sodium is very similar in properties 
to potassium. It is silver- white in color, and at ordinary 
temperature can be cut like wax. but below 0° C. it is hard. 
It is slightly lighter than water, its specific gravity being 
less than .97. and will float upon that liquid. It decom- 
poses water with liberation of hydrogen, but inflammation 
does not generally occur. If the water be warmed or the 
metal be placed on a slip of bibulous paper so that it will 
not move around, the temperature will rise sufficiently high 
to ignite the liberated hydrogen. The burning of the hy- 
drogen volatilizes some of the sodium, which gives a yellow 
color to the flame produced. Its action on water is not so 
energetic as that of potassium. 

Freshly cut sodium is very lustrous, but is immediately 
tarnished by exposure to the air. Sodium is a very im- 
portant reducing agent, its principal application being in 



METALLIC ELEMENTS. 231 

the preparation of magnesium, aluminum, and silicon from 
their chlorides. It also finds valuable application when 
amalgamated with mercury, such amalgam being more effi- 
cacious than mercury alone in extracting gold and silver 
from their ores. Much metallic sodium is now converted 
into sodium peroxide (Na 2 2 ), which has become a commer- 
cial product of great importance, being used as an oxidizing 
agent, especially in bleaching. 

SODIUM CHLORIDE ; COMMON SALT ; NaCl. 

Next to air and water this substance is the most essen- 
tial to the life and health of the animal world. In addi- 
tion to this it is one of the most important raw materials in 
the industrial arts. It is used in enormous quantities in 
the alkali industries, and is the primary source of nearly 
all the chlorine. 

Occurrence. Sodium chloride occurs widely and abun- 
dantly distributed. Immense deposits of it occur in various 
parts of the world. The waters of the oceans contain about 
three per cent of it ; the waters of many lakes and springs 
are impregnated with it. 

Preparation of Salt. In several countries salt is mined 
directly from the deposits." The most celebrated mine is 
that of Wielitzka, in Galicia, near Cracow. This mine has 
been worked for several centuries. It is also mined in Ger- 
many, in England, and at several places in the United 
States. Bock salt is mined in Louisiana, Kansas, and in 
Genesee, Wyoming, and Livingston counties, New York. 
Salt thus obtained is generally impure, and is purified by 
solution and recrystallization. 

The principal portion of the world's supply of salt is 
obtained by the evaporation of natural or artificial brines. 
Artificial brines are produced by admitting water to contact 
with the salt deposits and pumping it out after it has be- 
come heavily charged with salt. Both natural and artificial 



232 INORGAXIC CHEMISTRY. 

brines are often concentrated by exposing a large surface 
of the liquid to the air, and this, in Europe, is accomplished 
by allowing the liquid to trickle over walls or towers of 
brushwood. The concentration in suitable vessels is then 
continued by artificial heat or that of the sun. In some 
places in this country the evaporation is mainly by the 
sun' s heat alone, being carried on in shallow wooden vats. 
This is the process at Syracuse, X. Y., and in Bay and Sag- 
inaw counties, Michigan. At other places in these States 
the process is carried on entirely by artificial heat and is 
known as the pan-process. 

In warm climates, France especially, considerable salt 
is obtained by the evaporation of sea water. This is accom- 
plished in the marshes along the shore into which the water 
is admitted from the sea. As concentration is increased, 
the liquid is let from one basin to another until it reaches 
the crystallizing area. 

In cold countries salt is sometimes obtained from sea 
water by exposing the water in shallow pits and allowing 
it to freeze. A large portion of the water may thus be 
separated, and the solution left may be strong enough to 
pay for evaporation by artificial heat. 

In all these processes the purity of the salt depends 
upon the nature of the original brine, and other salts are 
often obtained from the brines left (mother liquor) after as 
much common salt has been obtained as practicable. The 
size of the grain of the salt depends upon the temperature 
at which the crystallization takes place, the lowest tem- 
perature giving the largest grains. 

Properties of Sodium Chloride. The properties of common 
salt are well known. Pure salt is very slightly deliques- 
cent ; the presence of magnesium and calcium chlorides 
greatly increase this tendency, and they are often present 
in table salt. It is soluble in a little less than three times 



METALLIC ELEMENTS. 233 

its weight of water at 0° C, and its solubility is very 
slightly increased by raising the temperature. 

Sodium Carbonate ; Na 2 C0 3 . Preparation. Before the French. 
Revolution this salt was obtained from the ashes of sea- 
weeds. The necessities of the French nation led Napoleon 
to offer a reward for the discovery of some other method for 
preparing it. This appeal was answered by Leblanc in the 
discovery of a method of making it from common salt 
which not only cheapened the production of sodium car- 
bonate but produced the most beneficial results upon many 
other manufacturing industries. It led to improvements 
in the manufacture of sulphuric acid ; it cheapened the 
production of hydrochloric acid and chlorine for bleaching, 
thus benefiting the manufacture of all textile fabrics ; it 
gave a tremendous impulse to the industries of glass- and 
soap-making. 

Leblanc Process. A full description of a manufacturing 
plant cannot be here attempted. Only the essential reac- 
tions involved will be given. The Leblanc process consists 
of three steps. 1st. The conversion of common salt into 
sodium sulphate by heating it with sulphuric acid : 

2NaCl + H 2 S0 4 = Na 2 S0 4 + 2HC1. 

The sodium sulphate is called the salt-cake, and the process 
the salt-cake process. 2d. The conversion of the sodium 
sulphate into the carbonate by heating it with powdered 
coal and limestone ; the reactions may be indicated by the 
equations, 

Na 9 S0 4 +C a = Na 2 S+2C0 2 ; Na 2 S + CaC0 3 = CaS + Na 3 C0 3 . 

The result of this process is called black-ash because of the 
dark color due to the carbon in the mixture of calcium 
sulphide and sodium carbonate. 3d. The last step in the 
process is the extraction of the sodium carbonate from the 



234 INORGANIC CHEMISTRY. 

black-ash by lixiviation with water, evaporation to the 
crystallizing point, and calcination. 

The salt thus obtained usually contains some common 
salt, some sodium sulphate, and some sodium hydroxide, 
the latter resulting from the action of the lime upon the 
sodium carbonate. To obtain pure carbonate the calcined 
soda is subjected to further treatment. 

Solvay's Process. This process, which has now largely 
replaced the Leblanc, depends upon the fact that if a solu- 
tion of the acid carbonate of ammonium be brought into 
contact with a saturated brine solution double decomposi- 
tion ensues, the less soluble acid carbonate of sodium being 
formed and crystallizing out, while ammonium chloride 
remains in solution. The result is accomplished by saturat- 
ing a strong brine solution first with ammonia and then 
with carbon dioxide, when the acid sodium carbonate is 
precipitated : 

JSaCl + NH 3 + C0 2 + H 2 = JNaHC0 3 + JN T H 4 C1. 



By heat the acid sodium carbonate is converted into the 
normal carbonate, 



2NaHC0 3 (heated) = ]STa 2 C0 3 + CO. + H 2 0. 

The C0 2 liberated in this operation is again used in the first 
step of the process. The NH 4 C1 is decomposed by lime and 
the ammonia is used again : 

2NH 4 C1 + CaO = CaCl 2 + 2NH 3 + H 2 0. 

The manufacture of the carbonates by the Solvay proc- 
ess at Syracuse, N. Y., and at Saltville, Va,, is now con- 
ducted on a large scale, also at Natrona, Penn., and Detroit, 
Mich. Other extensive works for this process are being 
erected at Cleveland. 

From the reactions indicated in the above processes it 
will be observed that in the Leblanc method the sulphur is 
finally left combined with calcium, forming calcium sul- 






METALLIC ELEMENTS. 235 

phide, and in the Solvay process the chlorine is left com- 
bined with the same metal, forming calcium chloride, both 
of which products are of themselves worthless. This waste 
of raw material is a loss in economy of manufacture, and 
methods have been devised by which the sulphur and 
chlorine are recovered for continual use. 

The carbonate is also prepared to a small extent from cryolite, which is 
a double fluoride of sodium and aluminum. 

Properties and Uses of Sodium Carbonate. The normal car- 
bonate crystallizes in oblique rhombic prisms containing 
ten molecules of water of crystallization (Na 2 CO 3 ,10Aq.). 
In dry air the salt effloresces and crumbles to a j)owder, 
losing the greater part of the water of crystallization ; when 
heated all the water of crystallization is driven off. The 
carbonate is very soluble in water. 

Water at 14° C. dissolves more than half its weight of the 10 Aq. salt. 
The solubility of this salt increases up to 36° C, but then decreases. At 
the boiling-point water dissolves nearly four times its weight of the salt. 

The salt is less soluble than potassium carbonate and is 
often called washing-soda. It is made in enormous quan- 
tities for use in the manufacture of glass and soap. 

The Acid Carbonate ; Bicarbonate ; KaHC0 3 . This salt is 
produced as described above in the Solvay process. It may 
also be produced by passing C0 2 into a solution or over 
crystals of the normal carbonate. It is used in medicine 
and quite extensively in the preparation of effervescing 
drinks. 

Both these carbonates are found impregnating the waters 
of certain lakes. Lake Mono is an example in our own 
country. Natural alkali in considerable quantity is obtained 
from California.* 

Sodium Hydroxide ; NaOH. This body may be produced 
by the action of slaked lime upon a solution of sodium car- 

* Immense lacustrine deposits of alkali are known to exist in Wyoming. 
These deposits are reported to consist of a large percentage of sodium sulphate. 



236 INORGANIC CHEMISTRY. 

bonate, the reaction being entirely similar to that for the 
preparation of potassium hydroxide : 

Na 2 C0 3 + Ca(OH) 2 = 2NaOH + CaC0 3 . 

Sodium hydroxide is very similar to that of potassium. 
It is the form into which the carbonate is generally con- 
verted preparatory to its use in the making of hard soap ; 
its solution is then called soda-lye. The hydroxide is now 
produced at many places from common salt by electrolysis. 

By the action of the electric current upon a solution of salt, the chlorine 
is liberated and an amalgam of sodium and mercury formed. By mechan- 
ical means the amalgam is transferred to another compartment of the 
cell containing water, there the sodium is transformed into the hydroxide 
and the mercury returned to the first compartment for re-amalgamation. 
In one compartment the mercury is the cathode, and in the other the 
amalgam is the anode. This method is employed at Saltville, Va., and at 
Niagara Falls. 

Sodium Nitrate ; NaN0 3 . This salt occurs abundantly na- 
tive associated with other salts, gypsum, and common salt. 
It is found in enormous quantities in Chili and Peru and is 
known as cubic nitre or Chili saltpetre. It is purified by 
solution and crystallization. The pure salt is deliquescent 
and very soluble in water. The deliquescent property 
prevents its use in black powder, but it is largely used in 
the manufacture of potassium nitrate and nitric acid. 

Borax, Sodium Biborate ; Na 2 0,2B 2 3 . This substance occurs as a 
native mineral under the name of borax or tincal. It is also obtained from 
other native borates. Tincal and other native borates are obtained in large 
quantities from the salines or marshes of southern California and Nevada. 
These marshes are remnants of former fresh water lakes. It also occurs 
abundantly in the waters of Clear Lake, California. In this state true 
veins of calcium borate have been found and worked for conversion into 
borax. Borax may be made by acting on sodium carbonate with boracic 
acid, and most of the borax of commerce is so made. 

Borax is an anhydro salt, and when fused dissolves many oxides, forming 
glassy beads which often have characteristic colors. This action makes it 
valuable in blowpipe tests in mineralogy; upon the same property 






METALLIC ELEMENTS. 237 

depends its use for soldering metals. It is now used in considerable 
quantities in glazing porcelain and earthenware and in making enamels. 

Sodium Silicate. An artificial combination of sodium and silica has 
long been used under the name of soluble glass. It can be made by fusing 
sand and sodium carbonate together, or boiling sand with a strong solution 
of caustic soda under pressure. 

This glass is used to coat wood and render it fire-proof, for wall-paint- 
ing, frescoing, and to make artificial stone. Sand moistened with it, 
pressed into moulds, dried, and highly heated, gives an artificial sand- 
stone, the sodium silicate fusing and acting as a cement. Any required 
color may be imparted by mixing the necessary metallic oxide with the 
sand. 

Sodium Thiosulphite ; Na 2 S 2 3 . This salt is largely used in photog- 
raphy. It is commonly known as sodium hyposulphite or simply "hypo.'" 
It is formed as stated on page 181 by digesting sulphur with a solution of 
sodium sulphite, Na 2 S0 3 . 

Sodium Sulphates. There are sulphates of sodium corresponding to 
those of potassium. The normal sulphate, ISra 2 SO 4 ,10Aq., known as 
Glauber's salt, is an intermediate product in the manufacture of the car- 
bonate. It has a bitter taste and is a strong purgative. The formula for 
the acid or bisulphate is NaHSO^Aq. 

Sodium forms several other compounds very similar to corresponding 
ones of potassium which will not be considered here. 

AMMONIUM; NH 4 . 

The similarity of certain ammonium compounds to anal- 
ogous compounds of potassium and sodium has already 
been mentioned. 

The compounds resulting from the action of acid oxides 
upon ammonia do not form these resembling salts until 
water is added. The true salts of ammonium are formed by 
the action of acids upon ammonia or by double decomposi- 
tion. Many such salts are closely analogous to and iso- 
morphous with those of potassium and sodium. In these 
salts the radical NH 4 is apparently substituted for hydro- 
gen and seems to play the same part as potassium and 
sodium in their respective compounds. 

The above and other similar facts have suggested the 



238 INORGANIC CHEMISTRY. 

possibility of the existence of a compound metal, which has 
been named ammonium. This radical, NH 4 , has never 
been isolated. 

An experiment first made by Berzelius adds some weight 
to the suj)position for the existence of a metallic radical. 
The amalgams of mercury have a metallic lustre, while the 
compounds of mercury with the non-metals are without 
lustre. Berzelius produced what was thought might be an 
ammonium amalgam with the usual metallic lustre; the re- 
sult tended to strengthen the belief in an ammonium metal. 
This amalgam may be produced by adding a little sodium 
amalgam to a solution of ammonium chloride; * a lustrous, 
porous, metallic-looking mass rises to the surface. This 
mass was once thought to be a true amalgam of mercury 
and ammonium, but it is now thought that the mercury is 
merely inflated by the ammonia and hydrogen from the de- 
composition of the ammonium chloride. The mass soon 
subsides, ammonia and hydrogen escaping. The similarity 
of the ammonium salts to those of sodium and potassium is 
the strongest support for the theory of a compound metal, 
and this similarity justifies the description of the salts at 
this place. 

SALTS OF AMMONIUM. 

The salts of ammonium are derived almost entirely from 
the ammoniacal liquor of the gas-works. This liquor con- 
tains an abundance of the carbonate and sulphide with 
other salts of ammonium. When the liquor is distilled 
with lime, the more stable base expels the ammonia, which 
is then collected as may be desired. 

Ammonium Chloride and Sulphate. These are the most 
common and important salts. To obtain the first, the am- 
moniacal liquor is distilled with lime, and the expelled 

* The sodium amalgam is readily prepared by adding a pellet of metallic 
sodium to a little mercury heated in a test-tube'. 



METALLIC ELEMENTS. 239 

ammonia is conducted into a vessel containing hydrochloric 
acid ; to obtain the sulphate, the gas is conducted into a 
vessel containing sulphuric acid ; in each case the gas is 
absorbed by the acid and the chloride or sulphate formed ; 
these crystallize from the acid. The chloride, NH 4 C1, is 
purified by sublimation and thus obtained as a tough, 
fibrous, and semi-translucent mass, difficult to powder. It 
has no odor, but has a sharp saline taste ; it is very soluble 
in water, producing great reduction of temperature. This 
salt is valuable in medicine and for many other purposes, 
and is the salt from which ammonia is generally obtained. 

The sulphate, (NH 4 ) 2 S0 4 , is manufactured in large quan- 
tity from the gas liquor, and is generally purified by solu- 
tion and recrystallization. It is largely used for the 
preparation of manures, of ammonium alum, and of other 
salts. A solution of it in ten parts of water is sometimes 
used to render cloth less inflammable ; muslins so treated 
will not burn with flame. 

Acid Ammonium Carbonate, Smelling Salts. This salt is 
usually obtained by distilling a mixture of ammonium 
chloride and sulphate with powdered calcium carbonate 
and collecting the distillate. This commercial carbonate is 
a mixture of the acid carbonate, (NH 4 HC0 3 ), and the car- 
bamate, (JN"H 3 ) 2 C0 2 . It is largely used in medicine and as a 
baking-powder. 

Sal volatile is an alcoholic solution of these salts. A 
strong solution of alcohol dissolves out the carbamate, 
leaving the acid carbonate. 

The normal carbonate is obtained from the commercial 
salt by treatment with strong ammonia. 

Ammonium Nitrate. This salt is prepared by adding am- 
monium carbonate to dilute nitric acid until neutraliza- 
tion has been reached. It can be made to crystallize like 
potassium nitrate ; it is very soluble, is deliquescent, 
easily decomposed by heat, and largely used in making 



240 INORGANIC CHEMISTRY, 

nitrous oxide. It is a constituent of some explosives : 
bellite contains it. 

Ammonium Sulphide. There are several sulphides of am- 
monium, the most important of which is believed to have 
the formula (NH 4 ) 2 S. It is a compound of great practical 
utility in the laboratory, often giving very characteristic 
precipitates with the solutions of many metallic salts. 

A solution of this substance is formed by saturating a solution of am- 
monia with hydrogen sulphide, and then adding another equal quantity of 
the ammonia solution : 

XH 2 + NH 3 + H 2 S = NELHS + XH 2 ; NH 4 HS + NH 3 = (NH 4 ) 2 S. 

The ammonia salts are all soluble and volatile and can 
be decomposed at high temperature. They are readily 
recognized by giving off ammonia when gently heated with 
lime, soda, or potash. 

OTHEK ALKALINE METALS. 

The other metals of this group are lithium, rubidium, and caesium. 
They are rare metals aud have not been usefully applied. Lithium has the 
smallest atomic weight and is the lightest of solid elements, its specific 
gravity being .59. 

Caesium was the first metal discovered by the use of the spectroscope. 
It is the most electro-positive of the metals. Its specific gravity is 1.88. 
Kubidium was also discovered by means of the spectroscope, immediately 
after the discovery of caesium. Its electro-positive qualities place it next 
after caesium. Its specific gravity is 1.52. 

Associated with the minerals in which the above metals are found are 
several other oxides, believed to be the oxides of rare metals. Their pres- 
ence has been determined by the spectroscope. Among them are the 
metals erbium, samarium, terbium, holmium. But little is known of the 
nature and properties of these bodies, and some of them are thought to be 
compounds. 

BARIUM ; Ba". 
Occurrence and Preparation. Barium occurs abundantly 
in nature as a constituent of heavy spar (BaS0 4 ) and with- 
erite (BaC0 3 ) ; these minerals frequently occur in the 



METALLIC ELEMENTS. 241 

gangue of lead mines. The metal finds no useful applica- 
tion; it is named from the great weight of its compounds 
{flapvcr^ heavy). 

It may be prepared by decomposing the fused chloride by the electric 
current. It is a yellow malleable metal and decomposes water at common 
temperature. 

Barium Chloride ; BaCl 2 . The chloride may be formed by 
dissolving the carbonate in hydrochloric acid and evapo- 
rating the solution. The solution of the chloride finds fre- 
quent use in the laboratory. 

Barium Sulphate ; BaS0 4 . Barium sulphate occurs abun- 
dantly native, as heavy spar. It is produced artificially as 
a precipitate whenever a soluble sulphate is brought to- 
gether in solution with a soluble barium salt. 

The sulphate is used considerably as a substitute for 
white lead under the name of permanent white. The native 
sulphate is not satisfactory for this purpose. The artificial 
is prepared from heavy spar by heating the powdered min- 
eral highly in contact with carbon, when the following in- 
dicated reaction takes place : 

BaS0 4 + C 4 = BaS + 4CO. 

The sulphide thus produced is soluble in water, and may 
Ibe used to precipitate the sulphate by the addition of dilute 
sulphuric acid. The artificial sulphate may also be pre- 
pared from the carbonate by acting upon it with hydro- 
chloric acid, and using a solution of the barium chloride 
thus formed to precipitate the sulphate, which is practi- 
cally insoluble in water. 

Barium Carbonate. The carbonate occurs native as witherite. It may 
be prepared artificially by precipitation, by adding an alkaline carbonate 
to a solution of the chloride, or by passing carbon dioxide through a solu- 
tion of the sulphide prepared as above described. The carbonate is prin- 
cipally used in the preparation of the other salts. 

Barium Nitrate ; Ba(N0 3 ) 2 . This salt is prepared by act- 
ing upon the carbonate or sulphide with dilute nitric acid 



242 INORGANIC CHEMISTRY. 

and evaporating to crystallization. It is used as a constit- 
uent of certain explosives and in pyrotechny. 

Barium Chlorate ; Ba(C10 3 ) 2 . This salt is prepared by act- 
ing upon the artificial carbonate with a solution of chloric 
acid ; it is used in pyrotechny. The salts of barium impart 
green color to flames. 

Barium Hydroxide ; Ba(OH) 2 . A solution of the hydroxide 
is used as a reagent in the laboratory. It is a delicate test 
for carbon dioxide, becoming turbid by a trace of the gas. 

The hydroxide may be prepared by dissolving the oxide in water, the 
oxide being obtained by heating the nitrate. On a large scale the hydroxide 
may be made by passing steam and carbon dioxide over the sulphide 
heated to redness, and decomposing the carbonate thus produced by super- 
heated steam ; the results are indicated by the following equations : 

BaS + C0 2 + H 2 = BaC0 3 + H 2 S ; BaC0 3 + H 2 = Ba(OH) 2 + C0 2 . 

Barium Sulphide ; BaS. Is prepared as above described. 
It has the property of shining in the dark after exposure 
to light; phosphorescence. 

Reactions of Barium Salts. Any soluble barium salt will 
give a precipitate, insoluble in nitric acid, with the solution 
of any soluble sulphate; upon this action is based the use 
of the nitrate and chloride in the laboratory. 

Alkaline carbonate or ammonium carbonate gives a 
white precipitate with the solution of a barium salt, insol- 
uble in excess but soluble in nitric acid. 

CALCIUM; Ca"; 39.8. 

Occurrence. Calcium has not been found in a free state 
in nature, but it is an abundant constituent of several min- 
eral compounds. Its compounds occur in many waters, 
and also abundantly in the animal and vegetable kingdoms. 
In the mineral kingdom its most abundant compounds are 
the carbonates, the silicates, the sulphates, phosphates, 
and fluorides; in organisms the compounds are mainly the 
phosphate, carbonate, and fluoride. 



METALLIC ELEMENTS. 243 

Preparation and Properties. Calcium was first prepared by Davy 
(1808) by the electrolysis of the chloride. It has a brass-yellow color, is 
harder than lead, and is very malleable. It decomposes water at the ordi- 
nary temperature, but not so readily as sodium and potassium. Its specific 
gravity is 1.58. It is not used in the metallic state. 

Calcium Carbonate ; CaC0 3 . This compound, in varying 
degrees of purity, exists in great abundance throughout the 
world. It forms rocky beds of limestone (marble, chalk, 
etc.) of immense thickness and extent. It is the chief con- 
stituent of the shells of mollusks, of egg-shells, and of coral 
formations. The wide distribution of this mineral, and its 
slight solubility in waters containing carbon, dioxide, ex- 
plain its presence in many waters which have already been 
described as hard- waters. In its different forms it is widely 
used as a building- stone and for interior decorations, and 
for the preparation of lime. It is useful in the extraction 
of iron from its ores and in many other metallurgic opera- 
tions. 

Lime ; CaO. No other metallic oxide is directly used so 
abundantly as lime. Lime is manufactured in enormous 
quantities by burning limestone, that is by decomposing 
the limestone by heat : 

CaC0 3 (heated) = CaO + C0 2 . 

The carbonate commences to decompose at a red heat, but 
the liberated carbon dioxide must be removed to continue 
the decomposition. The carbonate cannot be completely 
decomposed in a covered crucible. Lime is made in very 
large quantities in many parts of the world by heating lime- 
stone in rudely constructed kilns. The kilns employed are 
of various forms, but always so arranged that the escaping 
furnace gases pass over the heated stone, this being neces- 
sary for the removal of the liberated carbon dioxide. In 
the older furnaces the fires are kept up for two or three days 
and nights and then the furnace is allowed to cool and the 
lime raked out. In the modern continuous furnaces there 



244 INORGANIC CHEMISTRY. 

are two styles ; in one alternate layers of limestone and 
fuel are introduced into the furnace at the top, and the 
burned lime is removed from below ; in the other the fuel 
and limestone do not come into contact, there being fur- 
naces for the former and separate chambers for the latter. 
The stone is introduced above as the lime is raked out 
below. In all cases the limestone is broken into fragments 
of the proper size, otherwise complete decomposition does 
not take place in the interior of the kiln. In the great fire 
in New York City in 1835, marble columns that had been 
subjected to an intense heat were found unchanged beyond 
three inches from the surface. 

If the limestone contains much argillaceous or siliceous 
matter and has been too highly heated, it is found to con- 
tain glassy masses which refuse to slake ; the lime is then 
said to be dead burnt or overburnt and contains silicates. 
If the lime slakes but feebly it shows that it contains 
foreign substances, silica, clay, etc., and is then said to be 
a poor lime. If the lime combines readily with water 
largely increasing its volume (2£ times), evolves much heat, 
and crumbles to a fine powder, it is said to be rich or fat 
lime. Air -slaked lime, is that slaked by the moisture from 
the air. The process is necessarily slow, during which time 
the lime absorbs carbon dioxide as well as water ; such 
lime contains frequently one half its weight of .the car- 
bonate. 

Calcium Hydroxide ; Slaked Lime ; Ca(OH) 2 . This sub- 
stance is formed, as above stated, by treating fat lime with 
water : 

CaO + H 2 = Ca(OH) 2 . 

The hydroxide is slightly soluble in cold water, and its 
solubility decreases rapidly as the temperature increases. 
The solution is used in the laboratory for absorbing and 
detecting carbon dioxide in gases. It is readily converted 
into lime by the action of heat. 






METALLIC ELEMENTS. 245 

Slaked lime is used for numerous and important pur- 
poses. Its greatest use is in the preparation of mortar, and 
for this purpose it has been used from time immemorial. 
It is probably one of the first chemical compounds artifi- 
cially prepared by man. 

Ordinary mortar is made by mixing together slaked 
lime and sand. The hardening of mortar is due to the 
gradual conversion of a portion of the hydroxide into the 
carbonate. Not only does the mortar harden, but the whole 
forms a compact layer, attaching itself firmly to the stones 
between which it is placed. It is probable that the silica 
also in time combines with some of the lime, forming a 
silicate and binding the whole more firmly together. 

A mortar which has been exposed for only a few years 
contains more unaltered hydroxide than one of longer ex- 
posure ; for this reason structures of the middle ages display 
more solidity than more recent ones. The sand in mortar 
prevents excessive shrinkage and favors the penetration of 
the carbon dioxide. Unaltered hydroxide has been found 
in mortars of the Roman era. 

Freshly plastered houses are often uncomfortably damp 
because of the moisture which comes from the walls. The 
moisture is due both to the water mechanically mixed with 
the mortar, and to that set free chemically by the conversion 
of the lime into the carbonate : 

Ca(OH) 2 + C0 2 = CaC0 3 + H 2 0. 

The hardening of the mortar and the drying of the walls 
can be hastened by burning coke in open grates in the 
closed rooms. 

Note. — At 60° F. it requires 800 parts of water to dissolve one part of 
the hydroxide of calcium, and at 212° F. it requires 1500 parts of water to 
dissolve one of the hydroxide ; lime-water accordingly always gives a pre- 
cipitate when boiled. 

Anhydrous Calcium Sulphate ; CaSO*. This substance exists in con- 
siderable abundance in nature, occurring as a native mineral called 



246 INORGANIC CHEMISTRY. 

anhydrite. It is of little importance and cannot be applied to the uses 
which make the hydrous sulphate so valuable. The hydrous sulphate will 
now be described. 

Hydrous Calcium Sulphate; Gypsum; CaS0 4 ,2H 2 0. This 
compound is met with in considerable abundance in nature, 
and the many different varieties are included under the 
name of gypsum. Gypsum occurs in considerable abun- 
dance in natural beds. It is slightly soluble in water, being- 
most soluble when the water is at the temperature of 35° C. 
(1 part in 400). It is this substance in solution which pro- 
duces the permanent hardness of water already referred 
to. 

When gypsum is heated to near 200° C. it loses three 
fourths of its water, 

2CaS0 4 ,2H 2 = (CaS0 4 ) 2 ,H 2 4- 3H 2 0, 

and then constitutes plaster of Paris, so named because 
obtained in large quantities from quarries near that city. 
When the plaster of Paris is ground to powder and mixed 
with water to a paste, it combines with the water to repro- 
duce gypsum, evolving heat, expanding, and rapidly setting 
to a hard mass. If the gypsum is heated to above 200° C, 
all its water is driven off and it loses the property of taking 
it up rapidly again. Such overburnt gypsum is valueless 
for the use to which the ordinary plaster is put. 

The properties of the plaster give it many useful appli- 
cations. It is extensively used in making moulds and 
casts, statuettes, copies of coins, medals, etc., for the 
interior finish of walls and ceilings, and for the plaster 
.bandages of surgeons. Ten per cent of lime added to the 
plaster accelerates the setting and increases the hardness. 
If the plaster be moistened with a strong solution of alum 
instead of water, the setting is delayed and allows more 
time for manipulation. 

Stucco consists of plaster of Paris mixed with a solution 



METALLIC ELEMENTS. 247 

of glue or gelatine ; it solidifies more slowly and becomes 
hard enough to polish. Stucco may be given different 
colors by mixing with various metallic oxides. 

When plaster of Paris is exposed to moisture it regains 
part of its water and accordingly deteriorates in value. 

Plaster of Paris (burnt gypsum) is also a valuable fer- 
tilizer, its action is thought to be due to its power of ab- 
sorbing ammonia and volatile compounds of ammonium, 
thus rendering them more available for plant-food. 

Calcium Chloride; CaCl 2 . This compound is obtained as 
a by-product in certain chemical operations. It may be 
readily obtained by acting upon pure calcium carbonate 
with hydrochloric acid and evaporating the residue to 
crystallization. The powdered crystals mixed with snow 
or ice are used for the artificial production of cold. When 
the chloride has been highly heated (200° C.) it is very 
efficient in drying gases, and thus finds frequent use in 
the laboratory. 

Calcium Fluoride ; CaF 2 . This substance occurs as a natural mineral 
and is the most important source of hydrofluoric acid, already described. 

Calcium Sulphide ; CaS. This compound has the property of phos- 
phorescing after exposure to light, like barium sulphide. It is one of the 
constituents of certain luminous paints. The phosphorescence is not due 
to oxidation, since it is shown in a specimen that has been hermetically 
sealed for more than a century. It is now believed that the phosphores- 
cence is due to impurities, and that chemically pure sulphide does not 
show it. 

Other Compounds of Calcium. There are many other compounds and 
salts of calcium, the most common of which are the phosphates and the 
silicates. Certain of these are natural minerals, and are of great impor- 
tance in economic mineralogy and geology. 

Reaction of Calcium Salts. Solutions of calcium salts give 
a white precipitate with alkaline carbonates, insoluble in 
excess of the carbonate but decomposed by nitric acid. 
They give white precipitates with soluble oxalates, insolu- 
ble in acetic acid. 



248 INORGANIC CHEMISTRY.. 

MAGNESIUM; Mg". 

Occurrence. Magnesium is not found native, but occurs 
widely distributed as a constituent of many minerals. The 
most important of these are the carbonates and silicates of 
magnesium, more or less pure. Serpentine and talc are 
examples of the latter and dolomite of the former. Dolo- 
mite is a double carbonate of calcium and magnesium. It 
occurs in immense beds and forms entire mountain masses. 

Preparation, Properties, and Uses. The metal is now exclu- 
sively prepared by the electrolytic decomposition of the fused 
and dehydrated native carnallite, KCl,MgCl a ,6H 2 0. It is a 
silver- white metal, is malleable, but is ductile at only high 
temperature. It is pressed into wire in a semi-fluid state, 
and afterward flattened into ribbon, in which form it is gen- 
erally used. Its specific gravity is 1.75. It melts at a little 
below red heat, and is easily volatilized. In dry air it re- 
tains its lustre, but in moist air it soon becomes covered 
with a gray coating of oxide, which prevents further action. 

In the form of ribbon or wire it takes fire in the air a 
little above a red heat, and burns with great brilliancy, pro- 
ducing the oxide (MgO). To insure the combustion the 
unburned portion must be kept in the flame of the burning 
part or in contact with other flame. There are lamps spe- 
cially constructed to accomplish these results. 

The magnesium flame gives a continuous spectrum, 
which is rich in chemical rays (rays of great refrangibility). 
Because of this property the light may be used for photo- 
graphic purposes in the absence of sunlight. For photo- 
graphic purposes it has recently been largely superseded 
by electric light. It is still used extensively for signal- 
lights, and in flash-light cartridges for instantaneous pho- 
tography. 

Magnesia ; MgO. This is the only oxide of magnesium. 
It is always produced when magnesium is burned in air. 



METALLIC ELEMENTS. 249 

It is a white light powder, infusible except at the highest 
temperatures, and almost insoluble in water. It is a strong 
base and neutalizes acids in the most complete manner, 
though alkalinity is not shown by the taste. The oxide 
finds frequent use in medicine. On account of its infusi- 
bility it is largely used in making crucibles, cupels, and 
fire-bricks. For these manufacturing purposes it is ob- 
tained by roasting natural magnesium minerals. 

Magnesium Sulphate ; MgS0 4 ; Epsom Salts. The magnesium 
sulphate, the form known as Epsom salts, occurs in many 
mineral waters. It derives its name from the Epsom 
springs in England. It is abundant in Hunyadi water. 
This salt was formerly prepared by acting upon dolomite 
(double carbonate of calcium and magnesium) with sul- 
phuric acid. The calcium sulphate produced, being very 
insoluble, is easily separated from the magnesium sulphate. 
By far the greater portion of the commercial sulphate is 
now prepared from the native sulphate of the Stassfurth 
salt-beds. By exposing this native and nearly insoluble 
salt to the action of water it is converted into the soluble 
Epsom salts. The sulphate is used in medicine as a 
purgative, and largely as warp-sizing in the cotton trade. 

The composition of Epsom salts is expressed by the formula 
MgS04,7H 2 0. Of this water, six molecules are removed at 150° 0., while 
the remaining one is driven off at 200° C. The native salt of the Stassfurth 
beds called Kieserite has the composition MgS0 4 ,H 2 0. 

Other Compounds of Magnesium. There are many other compounds 
of magnesium, among which may by mentioned the chloride (MgCl«) and 
the hydroxide Mg (OH) 2 . The former occurs in many natural waters and 
is an important source of the metal. The hydroxide is much used in Europe 
for extracting sugar from molasses. 

The carbonate occurs as a natural mineral, magnesite, and the silicate 
occurs in talc, serpentine, mica, and several other minerals. The phos- 
phate of magnesium is present in small quantities in bones and in certain 
seeds. The borate also occurs in nature. 



250 INORGANIC CHEMISTRY. 

ZINC ; Zn"; 64.9. 

Occurrence. Native zinc has been reported from a few 
places (South Africa, Australia, and Alabama) but the 
reports lack verification. If found at all in the free state it 
is in very small quantity. It occurs quite abundantly as a 
constituent of certain natural compounds, the most im- 
portant of which are the common ores of zinc ; zinc oxide> 
ZnO ; zinc carbonate, ZnC0 3 ; zinc sulphide, ZnS. 

The mineralogical names for these ores are for the oxide, zincite ; for 
the carbonate, smithsonite or calamine ; and for the sulphide, zinc blende or 
sphalerite. 

METALLURGY OF ZINC. 

The extraction of zinc from its ores is simple in principle, 
but owing to certain properties of the metal, its reduction 
requires distinctive arrangements. Zinc is fusible and 
volatile at such moderate temperature, and so readily com- 
bustible in air, that its ores cannot be reduced like those 
of the other common metals, in an open furnace ; in such 
furnace the zinc would be volatilized and burned. 

If the ores to be used for the extraction of the metal are 
the carbonate and sulphide, they are first converted into 
the oxide. To accomplish this the carbonate is calcined to 
expel moisture and carbon dioxide. The sulphide is roasted 
for several hours with continual stirring, during which the 
sulphur is oxidized to sulphur dioxide and passes off. In 
each case the ore is left in the form of zinc oxide. 

The extraction of the metal from the zinc oxide is ac- 
complished by heating it with charcoal in specially con- 
structed vessels of fire-clay. The retorts are connected 
with suitable receivers of the same or different material, in 
which the zinc is collected. The carbon removes the 
oxygen from the ore, forming carbon monoxide, which 
escapes. The zinc volatilizes and is condensed in the 
receiver, the reaction being 

ZnO + C = Zn + CO. 



METALLIC ELEMENTS. 251 

At the beginning of the operation, before the receivers 
have become hot, the zinc deposits as a line powder, known 
as zinc-dust. This dust is a powerful reducing agent and is 
used in the arts as well as in the laboratory. As the pro- 
cess progresses, the zinc collects in drops and then in the 
liquid state and is removed at stated intervals. The zinc 
obtained from the condensers is usually impure, containing 
small quantities of the other metals, lead being the most 
frequent impurity. For purification, the spelter is remelted 
and the lead separated by virtue of its great specific 
gravity. 

In some of the modern furnaces the carbonate is intro- 
duced into the retorts without previous calcining ; the car- 
bon dioxide is driven off long before the temperature of 
reduction is reached in the retort. 

There are other methods employed for extracting zinc from the poorer 
varieties of ore. They may be included under the term "wet" processes 
and are not suitable for description here. 

Properties of Zinc. Zinc is a bluish-gray metal of well- 
known appearance ; it is a little lighter than iron, the 
specific gravity being about 7. Under ordinary circum- 
stances zinc is brittle, but between 120° and 150° C. it is 
malleable and may be rolled and hammered ; after such 
treatment it retains its malleability when cold. At 200° C. 
zinc again becomes brittle. 

Until the beginning of the century zinc was only used 
to form alloys, because, prior to that time, the manner of 
making it malleable was not known. At a bright-red heat 
zinc boils and volatilizes, and, if air be admitted, burns with 
a bluish-green light, producing zinc oxide. 

Zinc is soon tarnished in moist air, becoming coated 
with the oxide, which is gradually converted into a basic 
carbonate. The coating tends to protect the zinc from 
other action and renders it more durable. Commercial zinc 



252 INORGASIC CHEMISTRY. 

is readily acted upon by dilute acids and at the boiling 
temperature decomposes water. 

Pure zinc is not attacked by boiling-water, and is scarcely affected by 
either dilute or concentrated hydrochloric or sulphuric acid. Nitric acid 
and the alkalies attack pure zinc. Impure zinc amalgamated with mer- 
cury resists the action of the acids just as does the pure zinc. 

Uses of Zinc. Zinc is one of the highly useful metals. 
On account of its greater durability it is largely used to 
coat iron. Iron coated with either zinc or tin is commonly 
said to be galvanized. Zinc, while it lasts, acts more per- 
fectly than tin ; when tin is used, the protection is effective 
only so long as the surface of the tin is unbroken. As soon 
as the iron is exposed, the oxidation proceeds more rapidly 
than if the tin were not there. A coating of zinc protects 
so long as the zinc lasts. The difference in the action of 
these two metals is due to their different electrical relations 
to iron. By the above use of zinc, its durability is com- 
bined with the great strength of iron. 

The coating of iron plates with zinc is accomplished by 
producing a chemically clean surface on the iron and. then 
dipping it into melted zinc. To accomplish this, the sur- 
face of the melted zinc is covered with sal-ammoniac, which 
prevents the bad effects which would result from the zinc 
oxide there formed.* 

Zinc melts at a low temperature and its castings take a 
sharp impression of the mould. For these reasons it is 
used for many structural pmrposes where ornament rather 
than strength is considered. It has thus found general 
application in some countries for the preparation of statu- 
ettes, monuments, and other objects of beauty ; these can 
be bronzed or given any desired color. The recent process 
of photo-engraving consumes a considerable quantity of 

* The sal-ammoniac (NH 4 C1) dissolves some of the zinc, forming zinc 
chloride with liberation of ammonia. The zinc chloride dissolves the zina 
oxide and prevents any of it adhering to the iron. 



METALLIC ELEMENTS. 253 

specially prepared sheet-zinc. Zinc is used to a consider- 
able extent for roofing, guttering, and in electric batteries. 
Zinc-dust is used industrially and in the laboratory as a 
reducing agent. 

Zinc forms useful alloys with many metals, the most 
important of which are brass (copper and zinc) and German 
silver (nickel, zinc, and copper). 

Zinc Oxide ; ZnO. Zinc forms but one oxide, ZnO. The 
oxide occurs as a red mineral zincite. The native oxide is 
only used as an ore of zinc. The artificial oxide is formed 
by the combustion of zinc in air. The zinc fumes are led 
into condensing chambers, and the oxide is deposited as a 
powder. It is a white, tasteless powder usually called zinc* 
white. It is used as a paint, and while it has not the cover ^ 
ing power or body of white lead, it does not change color 
by the action of sulphuretted hydrogen, the sulphide oi 
zinc being white. Zinc- white is also used in pharmacy, and 
in the manufacture of certain kinds of glass. 

The oxide is a strong base, readily acted upon by acids, forming salta 
isomorphous with those of magnesium. When the oxide is heated it turns 
yellow, but is white again upon cooling. It is insoluble in water and very 
difficult to fuse. The oxide may be formed by decomposing the artificial 
carbonate by heat, the latter being precipitated from a solution of the sul- 
phate by means of an alkaline carbonate. 

Zinc Sulphate ; White Vitriol ; ZnS0 4 . The sulphate is pre- 
pared on a large scale by roasting the native sulphide in 
air at a comparatively low temperature. The sulphate 
formed is dissolved out with water and crystallized. The 
sulphate has a disagreeable taste, and is used medicinally 
as an emetic; it is also used in dyeing, in calico-printing, 
and in the manufacture of varnishes. 

The formula of the sulphate is ZnS0 4 ,7H,0. At 100° C. it loses all the 
water except one molecule. It requires a much higher temperature to 
expel this last molecule. 

Zinc Chloride ; ZnCL. The chloride is prepared by acting 



254 INORGANIC CHEMISTRY. 

upon zinc or zinc oxide with hydrochloric acid and evapo- 
rating to crystallization. It is very deliquescent, and its 
solution will dissolve paper and cotton. If zinc oxide be 
dissolved in a strong solution of the chloride, the solution 
will dissolve wool and silk. 

Burnett' s disinfecting fluid is a solution of zinc chloride. 
It absorbs sulphuretted hydrogen and ammonia and other 
offensive gases resulting from putrefaction. It is effective 
in arresting the decomposition of animal and vegetable sub- 
stances. The chloride is used as a caustic in pharmacy. 

Other Compounds of Zinc. Of the other compounds of zinc, the most 
important are the carbonate and the sulphide. Their occurrence and use 
as ores have already been mentioned. An hydroxide of zinc, Zn(OH) 2 , is 
precipitated whenever alkaline hydrates are added to solutions of zinc 
salts. A silicate and a phosphate of zinc occur as natural minerals. 

Reactions of Zinc Salts. Caustic potash, soda, and ammo- 
nia give a white precipitate, insoluble in excess. Ammo- 
nium carbonate gives a white jxrecipitate soluble in excess. 

Hydrogen sulphide gives no precipitate with solutions 
of zinc salts when free mineral acids are present. With 
neutral solutions, or with salts of the organic acids and 
zinc, the sulphide of hydrogen gives a white precipitate. 

Ammonium sulphide gives a white precipitate with solu- 
tions of zinc salts, insoluble in caustic alkalies. This white 
sulphide distinguishes zinc from all other common metals. 

CADMIUM. 

Cadmium sulphide, comparatively pure, has been found in a few places, 
but only in small quantities. Cadmium is generally present, in small 
quantities, in the ores of zinc, and is obtained from these ores. It 
is more volatile than zinc, and is found in the first portion of the dis- 
tillate that passes over in the reduction of zinc ores. When there is 
sufficient cadmium present with the zinc, this first distillate is collected 
separately for the extraction of the cadmium. 

Cadmium, in its volatility and chemical properties, resembles zinc, in 
appearance it is more like tin. It fuses at 320° C, and is useful for mak- 
ing fusible alloys. 



METALLIC ELEMENTS. 255 

Of the compounds of cadmium the most important is the sulphide. It 
may be prepared by the addition of sulphuretted hydrogen to a solution of 
a cadmium salt. It has a brilliant lemon-yellow shade, and is much used 
as permanent oil- and water-color. 

BERYLLIUM. 

Beryllium is a rare metal, whose oxide is found associated with silica 
and alumina in the different forms of the beryl. The metal resembles 
magnesium; its specific gravity is 2.1. 

ALUMINUM. 

Occurrence. Aluminum has not been found in the free 
state, but it is a widely distributed constituent of many 
natural mineral compounds. These compounds are simple 
or complex silicates, and the most abundant and important 
are clay, felspar, and the micas. The felspars are constitu- 
ents of many of the most common and important rocks, 
granite, gneiss, and others. By the natural decomposition 
of f elspathic rock clays of varying degrees of purity result, 
the purest form being known as kaolin. Pure kaolin is a 
hydrated silicate of aluminum. Common clay is kaolin 
mixed with sand and other impurities, and colored by iron 
oxide. Another important and frequently occurring natural 
compound containing aluminum as a constituent is cryolite, 
a double fluoride of sodium and aluminum. Aluminum 
sulphate, as a component of alum, is found in certain 
waters. Aluminum is one of the most abundant constitu- 
ents of the earth's crust. 

Preparation of Aluminum. Aluminum is now prepared 
mainly by electrolysis ; especially is this the method in this 
country. A powerful electric current is sent through a 
bath of cryolite (a double fluoride of sodium and aluminum) 
in which aluminum oxide (A1 2 3 ) is dissolved. The metal 
is deposited at the cathode, the cryolite being kept fused 
by the heat of the current. The alumina used is artificially 
prepared. 



256 INORGANIC CHEMISTRY. 

Until recently aluminum was prepared by reducing the double chloride 
of aluminum and sodium with metallic sodium. This method is still em- 
ployed to a certain extent in Europe. 

An electrical process for making aluminum alloy is used 
extensively in this country (Cowles' process). In this pro- 
cess the aluminum oxide is mixed with carbon and the mass 
subjected in a furnace to the passage of a strong current of 
electricity. Under the intense heat the oxide is reduced, 
but to collect the metal in a single fluid mass, it is found 
necessary to add copper or iron to the charge of the furnace, 
the alloys of these metals being then obtained. 

Properties and Uses of Aluminum. Aluminum is a remark- 
able metal in that its specific gravity is 2.56, yet it possesses 
many of the properties of the most useful metals. It is 
a white metal not acted upon by dry or moist air at the 
common temperature. It is very sonorous and has great 
tensile strength. It is ductile and malleable and can be 
beaten into leaf like gold and silver, but it requires fre- 
quent annealing during the operation. It is a good con- 
ductor of heat and electricity. It fuses at 625° C. and con- 
tracts upon solidifying. 

At high temperature it oxidizes in the air, and in the form of foil will 
burn in the air. Water and steam at high temperature act upon it. Nitric 
acid scarcely acts upon it at all nor does dilute sulphuric acid. Strong sul- 
phuric and hydrochloric acids act readily upon it. Organic acids do not 
affect it nor is it acted upon by mercury. 

As the price of aluminum falls its use is constantly ex- 
tending. In some countries many of the soldiers' equip- 
ments are made of this metal (cooking utensils, canteens, 
spoons, others parts of the mess-outfit, buckles, etc.). It 
has been experimented with for similar use in our service. 
A considerable quantity is employed in Germany for car- 
tridge cases to contain smokeless-powder, aluminum being 
much less rapidly corroded than copper. It is found admir- 
ably adapted for certain surgical apparatus (tubes, suture- 



METALLIC ELEMENTS. 257 

wire, supports, etc.) It can also be used to replace the 
more costly platinum in electric batteries. 

In addition to these uses of the pure metal, it is used as 
an alloy. The alloy with 80 parts of copper (aluminum 
bronze) approaches steel in strength. Other alloys of it 
are very strong and yet light. For engineering and sur- 
veying instruments the strong light alloys are admirably 
adapted. 

Aluminum Sulphate; A1 2 (S0 4 ) 3 , Aq. This salt may be 
prepared by acting upon aluminum hydrate with sulphuric 
acid and evaporating. The sulphate is prepared upon the 
commercial scale by acting upon clay with sulphuric acid. 
Clays (the hydrated silicates of aluminum) differ in their 
availability for the preparation of the sulphate. Bauxite 
is a variety of clay largely used for the purpose in England 
and in France. It is more easily acted upon by the acid, 
but contains more iron than China clay, or kaolin. 

The sulphate is largely used for the same purposes as 
the alums, which are next to be described. Indeed, it is the 
presence of this compound in the alums that gives them 
their industrial uses. The common alum (double sulphate 
of aluminum and potassium) is preferable to the single sul- 
phate for such uses because its crystalline form makes it 
more difficult to adulterate ; besides it is cheaper to pre- 
pare. 

Alum: Double Sulphate of Aluminum and Potassium; A1K(S0 4 ) 2 . 
Common alum is one of the most important artificial com- 
pounds of aluminum. This compound may be prepared by 
mixing solutions of the sulphates of potassium and alu- 
minum and evaporating to crystallization. 

Alum is generally prepared in one of two ways : 1st. 
By acting upon clay with concentrated sulphuric acid, by 
which aluminum sulphate is formed. Solution of this sul- 
phate and that of potassium sulphate are then mixed in 
proper proportions and evaporated to crystallization. 2d. 



258 INORGANIC CHEMISTRY. 

From alum shale, which is a shale impregnated with small 
crystals of iron pyrites. It also often contains bituminous 
matter sufficient to make it combustible. If the shale itself 
is not combustible it is mixed with some coal and made 
into long heaps. The piles of shale are then lighted and 
undergo a smothered combustion, which results in the 
formation of the sulphates of aluminum and iron. These 
sulphates are dissolved out and mixed with solution of 
potassium chloride, when double decomposition takes place 
between the iron and potassium salts with the formation 
of potassium sulphate and iron chloride. By evaporation 
the alum crystallizes from the solution.* The action in the 
shale heap consists in the oxidation of the iron pyrites with 
the formation of iron sulphate and sulphuric acid. The 
sulphuric acid attacks the clay, forming aluminum sulphate. 
In some cases with certain shales this action takes place 
by mere exposure to the air without any combustion. 

A considerable amount of alum is also made from the 
natural mineral alunite. This substance may be considered 
as a basic alum with more alumina than the common alum. 
By calcining and treating with water, common alum is dis- 
solved out, or by acting upon the alunite with sulphuric 
acid and adding the proper amount of potassium sulphate. 

The alunite may be considered as a compound of one molecule of 
anhydrous alum and one of aluminum hydroxide ; it may then be repre- 
sented by the formula, A1K(S0 4 ) 2 , Al(OH) 3 . 

Ammonium Alum. Ammonium sulphate may be used 
instead of the potassium salt in the preparation of alum, 
with the production of ammonium alum instead of potash 
alum. The two salts are entirely similar, except that the 
first contains the radical NH 4 instead of K. This alum is 
manufactured at certain places where the ammonium sul- 

* Potassium sulphate may be used instead of the chloride, but if there be 
much ferric sulphate an iron alum is formed which is isomorphous with and 
contaminates the potassium alum. 



METALLIC ELEMENTS. 259 

phate is cheaper than the potassium salt. The ammonium 
salt answers equally as well as the potassium salt in the 
most important applications of alum. At one time in Eng- 
land large quantities of this alum were made. 

Alum is very largely used in the preparation of pig- 
ments, as a mordant in dyeing and calico-printing, in paper- 
making, in clarifying water, and in the preparation of 
leather. Burnt alum, which is used medicinally, is pre- 
pared by heating common alum to a dull-red heat, driving 
off the water of crystallization. 

Alumina; Aluminum Oxide; A1 2 3 . Alumina is found in 
nature as corundum, a mineral next to diamond in hard- 
ness. Emery is an impure form of alumina. The ruby and 
sapphire are composed of nearly pure alumina. 

Alumina may be artificially prepared by strongly heating ammonium 
alum; the alumina is left as a white insoluble powder. Alumina is a very 
weak base, so that its salts may exhibit acid properties. 

Aluminum Hydroxide; Al 3 (0H) 6 . If solutions of aluminum 
salts (alum may be used) be treated with ammonia or an 
alkaline carbonate, a white gelatinous precipitate of the 
hydroxide is formed, which may be dried to a soft, friable 
mass. This hydroxide has a very powerful attraction for 
organic matter, and when digested with solutions of vege- 
table coloring matters it combines with and carries down 
the coloring matters, leaving the liquid clear, if the hydrox- 
ide be in sufficient quantity. The compounds resulting 
from the combination of the hydroxide and the coloring 
matters are called lakes. The fibres of cotton may be im- 
pregnated with the hydroxide and can then be permanently 
dyed. The aluminum compound has affinity both for the 
fibre and the coloring matter. Bodies thus used to fix the 
coloring matters are called mordants, hence the use of alu- 
minum salts as mordants. Other salts of aluminum have 
this property, and it will be again noticed. 



260 INORGANIC CHEMISTRY. 

Other Compounds of Alumina. The silicates of aluminum form a 
large and important class of minerals as already stated. Among the less 
important compounds of this element are the chloride, fluoride, and sul- 
phide. 

OTHER METALS OF THE ALUMINUM GROUP. 

Thallium. This element was discovered in 1861 by means of the 
spectroscope. Its discovery was among the first applications of the spec- 
troscopic method. Thallium resembles lead in its physical properties, in 
the character of its sulphide, and of its haloid salts. It resembles the 
alkali metals in the solubility of its hydroxide and carbonate. Its chloride 
is nearly insoluble, in which it is related to silver, but because of the rela- 
tion between its properties and its atomic weight, it is classed with the 
aluminum group. None of its compounds have found useful application. 
Thallium salts are poisonous and impart a green color to flame. 

Gallium and indium are generally found accompanying the ores of zinc 
and are obtained from this source. Neither the metals nor their salts have 
found any important applications. 

The other metals of the aluminum group, falling in the odd series, are 
the rare elements scandium, yttrium, lanthanium, ytterbrium. The im- 
portance of these bodies is not sufficient to warrant a description here. 

IRON; Fe"; 55.5. 

Occurrence. Iron is the most useful of the metals. It is 
only rarely found in the metallic or pure state. Metallic 
iron is usually the chief constituent of meteorites, those 
metallic masses which occasionally fall upon the surface of 
the earth. Meteorites generally contain several other ele- 
ments, among which are nickel, cobalt, and chromium. 
Meteorites weighing as much as twenty tons have been 
found. Native iron has also been found disseminated in 
grains and in large masses through certain igneous rocks. 

As a constituent of natural compounds iron is very 
widely diffused. It can be detected in nearly all rocks, in 
many minerals, and is present in the coloring matter of 
common clays and soils. The oxides, carbonate, and sul- 
phide of iron are found abundantly and constitute the 
ores of iron. 



METALLIC ELEMENTS. 261 

ORES OF IRON. 

Ores of a metal are those natural compounds which 
are worked to obtain the metal. The ores of iron are the 
following : 



Chemical Name. Common or Mineral Name. Composition. 

< Ferric oxide or { Haematite or i F O 

\ Iron sesquioxide, ( Specular iron ore, ] e2 3 ' 

Ferroso-ferric oxide, Magnetic oxide or magnetite, Fe 3 4 . 

Ferric hydrate, Limonite or brown haematite, 2Fe 2 08,3H 2 0. 

Ferrous carbonate, Spathic ore j ^ckbanT ( FeC0 - 

Iron bisulphide, Iron pyrites, FeS 2 . 

These ores frequently contain impurities. The spathic 
when mixed with clay is known as clay ironstone, when 
with bituminous matter it is called blackband. Other im- 
purities are often present which must be wholly or partially 
removed in the manufacture. Compounds of sulphur and 
phosphorus are common, and are very objectionable in the 
ores. Pyrites is seldom used as an iron ore, but is more 
generally worked for the sulphur. 

METALLURGY OF IRON. 

This important branch of industry usually consists of 
two distinct operations. 1st. The production from the ores 
of a fusible carbide of iron (cast iron). 2d. The conversion 
of the cast iron into pure iron (wrought or bar iron). Iron 
is, however, made direct from the ore. 

Cast or Pig Iron. Cast iron is made by subjecting the 
ores of iron to the action of reducing agents in a blast fur- 
nace, but certain classes of ores often undergo a preliminary 
treatment before being introduced into the blast furnace. 

Preliminary Treatment of Ores. This treatment consists in 
sorting the ore, breaking it into fragments of the required 
size, and subjecting it to a calcination or roasting process. 
The effects of the calcination are : 1st. To drive off water 
when present in too large quantity. 2d. To drive off sul- 



262 INORGANIC CHEMISTRY. 

phur, arsenic, and other volatile impurities. 3d. To drive 
off carbon dioxide from spathic ores and remove carbon- 
aceous matter from the blackband when there is an ex- 
cessive amount and convert them into ferric oxides. 4th. 
To leave the ore in more porous and in better condition 
for the action of the reducing agents in the furnace. 

This preliminary treatment is seldom applied to the 
haematite and magnetic ores unless they contain impurities. 
The calcination of the ore is often accomplished in open 
heaps or in rectangular chambers, but in the most modern 
method the calcining is conducted in large circular kilns, 
the ore and fuel being charged in at the top, the process 
being continuous. 

The Furnace. The furnaces in which the ore is reduced 
differ somewhat in form and size, depending upon the na- 
ture of the ore and fuel employed. The capacity of fur- 
naces varies from 15,000 to 50,000 cubic feet, the best 
modern furnaces having between 20,000 and 30,000. The 
height varies from 40 to 100 feet, the most recent furnaces 
being not over 85 feet. Fig. 10 shows a section of a modern 
American furnace, being that of one of the furnaces of the 
Edgar Thompson works. This figure also illustrates the 
manner in which furnaces are now supported, upon an iron 
frame resting upon piers. The furnace is jacketed through- 
out with plates of iron or steel riveted together ; it is lined 
with fire-brick, these being surrounded by common brick 
or stone. In nearly all modern blast furnaces the top of 
the furnace is closed by some such arrangement (cup and 
cone) as is shown in the figure. This serves to prevent the 
escape of the gas from the top of the furnace and for the 
better distribution of the ore, fuel, etc., charged in at the 
top. 

The heated gases are drawn off at the top by large pipes 
which lead from the furnace near the top, above the stock- 
line; these pipes are known as down-comers. The gases are 



METALLIC ELEMENTS. 



263 



used as a source of heat for the air fed to the furnace and 
for other purposes. Heated air is forced into the furnace 
through delivering tubes called tuyere-pipes, one of which 
is shown at T in the figure. The temperature of the tuyere- 
pipe is kept down by causing water to circulate through a 
truncated cone which surrounds it. Arrangements are al- 
ways connected with the furnace for delivering the re- 



t & 8 0/4CO=F44CO r - 



6Rp*'2CO«=Fe | C+C0 2 - 



C0 2 +C=2CO 
C-*-0=CO, 




Fig. 10. 



quired quantities of raw materials at the top. For intro- 
ducing the materials, the top of the furnace is entirely or 
partially surrounded by a charging gallery and the mate- 
rials are carried up by some form of hoist or lift, unless the 
furnace is so situated that the gallery can be reached by 
bridge or trestle from higher ground. The slope of the 
furnace is that which experience has shown to be the best 
for the production and r^roper distribution of the required 



264 INORGANIC CHEMISTRY. 

temperature conditions, and for the proper movement of the 
materials charged into the furnace at the top and bottom. 

The Fuel. The fuels used in blast furnaces are coke, 
anthracite coal, charcoal, and in certain localities some 
varieties of bituminous coal. 

Reduction of the Ore. When the furnace is first started 
it is said to be Mown in. For this purpose the furnace is 
charged with coke or coal, with wood at the bottom. A 
gentle blast is first employed so as to gradually raise the 
temperature and to produce regular expansion in drying. 
When the fuel has descended by burning to the proper dis- 
tance there is introduced a charge of the iron ore mixed with 
flux (usually limestone), when the latter is necessary. Over 
this is placed a charge of fuel, then a second layer of ore 
and flux, and so on in alternate layers until the furnace is 
full. It is usually several months before a full charge is 
employed in a furnace. The principal steps in the reduc- 
tion in a coke furnace may be outlined as follows. 

The hot blast from the tuyere-pipes gives up its oxygen 
to the carbon of the fuel with which it first comes in con- 
tact, producing carbon dioxide. The carbon dioxide is 
very quickly decomposed by the excess of red-hot carbon, 
forming carbon monoxide, so that at a very short distance, 
not over three feet from the tuyere-pipes, no free oxygen 
or carbon dioxide is found in the ascending blast. At a 
short distance from the tuyeres the gaseous current is com- 
posed of about one third carbon monoxide and two thirds 
nitrogen. The nitrogen is chemically inert, but the carbon 
monoxide has great reducing power, and as it comes in 
contact with the descending heated iron oxide it removes 
the oxygen from the oxide, leaving metallic iron and form- 
ing carbon dioxide. This change takes place in what is 
called the upper reducing zone of the furnace, and may be 
approximately stated as embracing the upper third of the 
furnace. 



METALLIC ELEMENTS. 265 

Just below this zone the carbon dioxide of the limestone 
is driven off. 

The lime, clay, sand, and other impurities of the gangue, 
together with the metallic iron and coke, continue the 
descent, growing hotter and hotter. In this descent below 
the upper zone the principal and most important action 
which takes place, is the removal of some of the carbon 
from the gaseous carbon monoxide by the iron, with the 
production of carbon dioxide and the formation of iron 
carbide or cast iron. When the material of the furnace 
has descended to the level a little above that of the tuyere- 
pipes, a temperature is reached at. which the silica reacts 
upon the lime and other bases, producing a slag composed 
of fusible silicates. It is in this region of the furnace that 
the oxides of silicon, sulphur, and phosphorus are reduced 
and these bodies enter the iron. The iron itself here 
reaches the f using-point, and the entire charge is fused and 
flows down into the hearth, settling in two layers beneath 
the tuyere-pipes, the slag on top. The region in which 
the oxides of silicon and phosphorus are reduced and the 
changes just referred to take place, is frequently called the 
lower reducing zone. For convenience in description we 
shall call the region between the upper and lower reducing 
zones the middle zone. 

There is an upper tap-hole through which the slag is 
allowed to run off. The iron is drawn off at the lower hole 
at stated intervals. The slag, which has about six times 
the bulk of the iron, is made to run off to the most favor- 
able point for removal from the vicinity of the furnace. 
The iron runs out into sand or iron moulds, forming rough 
cylindrical masses weighing about one hundred pounds 
(called pigs), and the term pig iron is generally used as 
synonymous with iron direct from the furnace. The 
changes which take place in the different parts of a coke 
furnace may be summarized as follows : assuming the iron 



266 INORGANIC CHEMISTRY. 






ore to be magnetite, this being the form to which all the 
ores pass soon after entering the furnace, then in the upper 
reducing zone the reaction is 

Fe 3 4 + 4CO = Fe 3 + 4C0 2 ; 

in the middle zone it is 

Fe 5 + 2CO = Fe 5 C + C0 2 ; 

between the tuyeres and the lower reducing zone the reac- 
tions are 

C0 2 + C = 2CO and C + 2 = C0 2 . 

The description above given for reducing ores applies 
to a modern coke furnace. When other fuel is used the 
shape and dimensions of the furnace are usually different 
and the reactions occurring in the furnace are somewhat 
differently distributed. By the use of selected ores and 
fuel, and by special treatment in particular furnaces, the 
nature and quality of the iron are under considerable con- 
trol. 

In the middle zone, as above designated, it is pretty well established 
that the metallic iron takes oxygen from some of the carbon monoxide, 
forming iron oxide and depositing solid carbon. At the high temperature 
of the lower reducing zone the solid carbon takes an active part in reduc- 
ing the oxides of silicon, sulphur, and phosphorus. Some able authorities 
assign much importance in this lower zone to the reducing action of the 
metallic cyanides which are known to be formed in the vicinity of the 
tuyere-pipes. 

Slag and Fluxes. All ores contain more or less extrane- 
ous matter, and it would be impossible to separate the iron 
from these impurities unless they were brought to a liquid 
state. The extraneous matter after fusion constitutes the 
slag. If the impurities of the ore are not of such material 
as will fuse at the temperature of the furnace, other mate- 
rials are added to bring about this result; the added mate- 
rial is known asjlux. The principle which governs the addi- 
tion of the flux is that complex silicates are more readily 



METALLIC ELEMENTS. 267 

fusible than simple ones. If the natural matter accompany- 
ing the ore, usually called gangue, be clay (silicate of alu- 
minum), limestone is added as a flux. This provides for 
the formation, at the temperature of the furnace, of a double 
silicate of calcium and aluminum, which is more fusible 
than clay. If the gangue be silica, both clay and limestone 
are added, the object being in each case to form fusible 
double silicates of aluminum and calcium. When silica 
is in excess in the slag there is great loss of iron by the 
formation of iron silicate. 

It may in general be stated that for each ton of iron 
produced there is also a ton of slag, and the bulk of the 
slag is about six times that of the iron. It thus becomes a 
serious problem, in many places, to dispose of the slag pro- 
duced at the furnaces. The slag is removed from the fur- 
nace in the most expeditious way, and this of course de- 
pends upon the location of the furnace. It is often drawn 
off into bogies or trucks running on rails, the trucks being 
so arranged that the blocks of slag are easily removed when 
solidified. In this country at some furnaces side-tipping 
ladles lined with fire-brick are used to receive the slag, the 
ladle being mounted on trucks. With small furnaces the 
slag is usually run off into rough sand moulds, from which 
it is removed when sufficiently cool. 

Uses of the Slag. Slag has been used for macadamizing 
roads, especially when suitable stone is not readily obtain- 
able, and for ballasting railways. Cast into blocks it has 
been used for breakwaters, and occasionally for founda- 
tions of light structures; certain slags cast under proper 
conditions have been used for paving-blocks and for brick. 
The granulated slag, which is produced by allowing melted 
slag to trickle into water, makes a good brick when mixed 
with one eleventh its weight of lime and pressed into shape. 
This slag ground to fine powder and mixed with lime 
yields an hydraulic cement. Slag-wool or mineral-wool is 



268 INORGANIC CHEMISTRY. 

produced by blowing a jet of steam into the melted slag ; 
this mineral-wool is non-inflammable and a non-conductor 
of heat. 

The utilization of the slag is accomplished on a large scale 
in Germany, both in the production of brick and cement. 
In 1892 there were reported in that country ten slag-cement 
factories with a total production of 600,000 tons of cement. 
Slag cement has not been made in this country. The slag 
run off from all the American furnaces during some of the 
most prosperous years would cover an area of a square mile 
to the depth of eight feet. 

Furnace Gases. The gases which are led off from the top 
of the furnace through the down-comer pipes besides being 
hot are highly inflammable. They consist of nitrogen 
(amounting to something over one half by volume), carbon 
monoxide (about one fourth by volume), and Carbon di- 
oxide (about one fifth by volume). These gases are con- 
ducted off and used as a source of heat for generating 
power, or more generally for heating the air which is to be 
fed to the furnace. For the latter purpose the escaping 
gases from the blast furnace are conducted into suitable 
stoves or furnaces where the proper amount of air is ad- 
mitted for the combustion of the carbon monoxide. The 
best modern stoves may be said to consist of a closed cham 
ber containing a volume of brickwork so arranged as to 
expose a large absorbing surface to the heated gases. When 
the absorbing material of the stove has become heated the 
furnace gases by suitable valves are shunted to another 
stove, while the air to feed the furnace is driven through the 
first. The air to feed the blast-furnace absorbs the heat 
given out by the gases which have already passed through 
the heating furnace. In this way the temperature of the 
blast can be raised to the desired extent. The blast fre- 
quently enters the tuyeres at the temperature of 800° or 900° 
C, and under a pressure of from five to twelve pounds. 



METALLIC ELEMENTS. 269 

Some of the best chambers used to heat the blast contain brick so piled 
as to expose as much surface as possible. The Whitwell stove is divided 
by a series of partition walls in close proximity, built of fire-brick. The 
gases in their transit through the stove pass one wall at the top and the 
next at the bottom. In the Cooper stove hexagonal, honeycombed brick 
are stacked so as to make many flues through which the hot gases and 
air alternately pass. 

These stoves may be used to heat gaseous fuel as 
well as the air for its combustion, when such fuel is em- 
ployed. Gaseous fuel is prepared for certain operations in 
a manner similar to that for preparing water gas and by 
the incomplete combustion of carbon ; such gaseous fuel is 
generally known as producer gas and consists mainly of 
carbon monoxide or of this with hydrogen. When the 
producer gas and the air for its combustion are both raised 
in temperature by passing through stoves, and the stoves 
themselves heated by the products resulting from the com- 
bustion, it constitutes the system of regenerative firing. 
By it very high temperatures can be obtained. Regenera- 
tive firing was the invention of Siemens. 

From the above description it will be observed that the blast furnace is 
fed at the top with solid material, ore, flux, and fuel, which form a 
continually descending column. It is fed at the bottom with air, which 
continually passes upward in an ascending current. The total weight of 
the ascending current is about the same as the descending column. Some 
of the larger American furnaces use in 24 hours 550 tons of ore, 450 tons 
of coal, 150 tons of limestone, and over 1000 tons of air. Such furnaces 
yield about one ton of iron for each ton of fuel. 

COMPOSITION AND PROPERTIES OF CAST IRON. 

The iron direct from the blast furnace is generally 
designated as pig iron ; after remelting it is called cast 
iron. This distinction is that of the foundry and not that 
of the laboratory. Chemically, pig iron is a particular 
variety of cast iron. Average cast iron contains from 90 to 
95 per cent of iron and from 2 to 5 per cent of carbon, the 
remaining constituents generally consisting of silicon. 



270 INORGANIC CHEMISTRY. 

sulphur, phosphorus, and manganese, the silicon being 
the most abundant of these. Of these ingredients of the 
cast iron the carbon and sulphur are derived from the 
fuel, the silicon, phosphorus, and manganese from the 
ore. 

The two varieties of cast iron most generally distin- 
guished are the white and gray. These varieties are based 
upon the condition of the carbon present in the solid 
metal. Fused iron dissolves and chemically combines 
with the carbon, and if all or nearly all of the carbon is 
retained in combination after solidification, the metal has 
an almost silvery fracture and is known as white iron. 
On the other hand if a portion of the carbon separates 
from the iron on cooling, in the form of minute graphitic- 
like crystals, the metal will have a dark gray color due 
to the separated carbon ; this form is the gray iron. A 
variety intermediate between these two is called mottled 
iron. 

The difference of condition of the carbon in the white 
and the gray iron is shown when specimens of each are dis- 
solved in dilute sulphuric or hydrochloric acid. In the 
gray iron the separated carbon remains unaltered, while 
in the white the constituent carbon passes off in combina- 
tion with hydrogen, yielding hydrocarbons, often observed 
by their disagreeable odor. 

The properties of the two varieties of iron are very dif- 
ferent. The white iron is slightly heavier, is much harder, 
and f uses at a much lower temperature. The gray iron is 
soft enough to be cut in a lathe, and is more fluid when 
fused than the white and is therefore better for casting. 

The condition of the carbon in the iron depends partly 
upon the rate of cooling of the melted metal, and partly 
upon the proportions of the other constituents present. 
Pure iron fused in contact with carbon is capable of com- 
bining with nearly five per cent of that element, but the 



METALLIC ELEMENTS. 271 

amount of carbon that will be taken np depends upon the 
other constituents of the fused iron. Manganese increases 
the amount of the carbon dissolved by the iron, while sili- 
con and sulphur decrease the amount. In the cooling of 
the melted iron, manganese and sulphur tend to prevent 
the separation of graphitic carbon, while silicon tends to 
cause this separation ; accordingly white iron usually con- 
tains less silicon than gray. 

If sulphur and manganese be present in the melted iron, it will more 
likely solidify as white iron. The effects of the manganese and silicon are 
the same both upon the melted and the cooled metal, but the sulphur tends 
to prevent the combination of the carbon with the melted iron, and to cause 
it to combine with the solid iron. Phosphorus is thought to prevent the 
separation of graphite, but to a less extent than sulphur. 

The condition of the carbon in the solid iron can be 
materially modified by the rate of cooling. Rapid cooling 
prevents the separation of the carbon from the iron, and 
slow cooling favors the separation ; the first accordingly 
promotes the production of hard white iron, and the latter 
that of gray iron. Chill-casting is brought about by virtue 
of the foregoing facts. Objects cast of soft gray iron may 
thus be made very hard externally by rapid cooling. If 
any particular portion of a casting is required to be hard, 
the corresponding part of the mould is made of a good con- 
ducting material so as to rapidly cool that part. When 
white cast iron is melted and cooled very slowly it becomes 
gray. 

The minor varieties of cast iron grade into each other, 
and it is difficult to specify in every case the variety to 
which a specimen belongs. For commercial purposes there 
are several grades of cast iron, the dark gray being number 
1, and the hardest white iron being number 8. 

Cast iron is the most fusible variety of iron. It is neither 
malleable nor ductile nor can it be tempered. It is hard 
and brittle, as already stated ; it may contain as much as 



272 INORGANIC CHEMISTRY. 

seven per cent of other elements. Its tensile strength is 
small as compared with wrought iron and steel, and its 
application for constructional purposes is much more lim- 
ited than these latter. 

WROUGHT IRON. 

Wrought iron may be denned as commercially pure 
iron; it is not chemically pure, as it contains something 
less than .15 per cent of carbon, with minute proportions 
of sulphur, silicon, and phosphorus. 

Manufacture of Wrought or Malleable Iron. Wrought iron 
is now made by two processes : 1st. By the direct process, 
directly from the ore ; 2d. By the indirect process, by the 
purification of cast iron. The indirect method is that most 
generally followed and will be first described. The prin- 
ciple of the more common process, known as the puddling 
process, will be given first. 

Puddling The puddling is conducted in a reverbera- 
tory furnace, in which cast iron is subjected to a purifying 
process, the carbon, phosphorus, sulphur, silicon, etc., being 
oxidized and removed. The general form of the furnace 
used is shown in Fig. 11, the operation being conducted 
as follows : The bottom and sides of the furnace bed are 
covered with fettling, consisting of slags rich in iron sili- 
cate, or with such slags mixed with iron oxide. Five or 
six cwt. of pig iron are charged into the furnace, the doors 
closed and the drafts turned on. When the iron is 
melted it is well rabbled or stirred, so that every part of it 
is brought into contact with the oxide. Very soon the 
iron boils violently in consequence of the escape of carbon 
monoxide. After the boiling stage the metal drops or 
comes to nature and the whole mass becomes pasty. Slag 
or tap-cinder is drawn off during and at the end of the 
operation. 

The silicon, manganese, and phosphorus are separated 



METALLIC ELEMENTS, 



273 



mainly during the melting stage and pass into the slag. 
During the boiling of the iron the carbon is removed and 
also a further portion of phosphorus. The sulphur is 
mainly eliminated in the slag in the form of iron sulphide. 
The pasty iron is balled up by the puddler into masses 
weighing from fifty to one hundred pounds, which are 
removed from the furnace and subjected to the action of a 




Fig. 11. 

steam-hammer. The hammering presses out the slag and 
causes the pasty particles of iron to cohere, forming an 
oblong mass or bloom. The bloom is passed through 
rollers and pressed into puddled bars, but these bars are 
not yet fit for use. The puddled bars are cut up and made 
into bundles, reheated in the mill furnace, withdrawn at the 
welding heat, and passed through rollers until the required 
dimensions are obtained. By this operation the texture 
of the iron is made more uniform, a fibrous structure 
imparted, and the quality generally improved. This 
product is commonly known as merchant bar. If the 
merchant bar be doubled upon itself, heated and rolled, 



274 INORGANIC CHEMISTRY. 

it gives the best iron, bar or wire iron. These operations 
improve the quality of the iron by pressing out more of 
the slag, and appear to produce a slight chemical effect by 
removing by oxidation some of the impurities of the iron. 

In the puddling operations just described the impurities 
of the cast iron are oxidized mainly by the oxide of iron 
used in the hearth, though the oxygen of the air exerts 
some action. It is quite customary to add a little iron oxide 
or a mixture of iron and manganese oxides with the charge, 
or after the metal has been melted. These also take part 
in the oxidation of the impurities. The puddling furnaces 
were originally lined with siliceous material, but experience 
has led to the basic lining. 

This puddling process is often spoken of as the pig-boil- 
ing process because the metal is so thoroughly liquefied 
and presents the appearance of violent boiling when the 
carbon monoxide is escaping, The whole operation usually 
occupies from one and a quarter to one and a half hours. 

The puddling process was formerly, and is yet sometimes, preceded by 
a refining operation. The refining consists essentially in subjecting the 
fused metal to a draft of air by which a portion of the iron is oxidized. 
The iron oxide reacts upon the impurities of the iron, largely removing the 
silicon and sulphur, and some of the phosphorus. The refined iron then 
remaining is puddled upon the hearth of a reverberatory furnace very 
similar to that used in the pig-boiling process. Formerly the impurities 
of the refined iron were oxidized largely by the oxygen of the air, and the 
iron did not become liquid as in the pig-boiling process. It was therefore 
known as dry puddling. The refining and dry puddling of the iron are 
not now generally practised. 

Mechanical Puddling. Owing to the heavy manual labor 
involved in the puddling operations described and to the 
desire to cheapen the process, several attempts have been 
made to effect mechanical puddling. 

Dank's rotating puddling furnace, an American inven- 
tion, was one of the most successful of these. The puddler 
consists of a large cylinder arranged to rotate about its 



METALLIC ELEMENTS. 275 

horizontal axis. The inside of the cylinder is lined with 
fettling, iron oxide, and lime. The name-gases from the 
heating furnace enter the cylinder at one end and pass out 
at the other. The cast iron to be puddled is run into the 
cylinder in a liquid state and the puddling is accomplished 
by rotating the cylinder by mechanical means. The results 
reached are brought about by the same chemical actions 
described in the pig-boiling process. This furnace has been 
gradually abandoned both in this country and Europe and 
is no longer in general use. 

WROUGTH IRON DIRECT FROM THE ORE. 

The earliest wrought iron was undoubtedly obtained 
direct from the ore, and bar iron is still to a limited extent 
obtained in the same way. In these early methods the 
ore -was heated in contact with the fuel under the action of 
the simple blast, the air being blown in with a hand- 
bellows ; in India to-day this method is followed. The 
American bloomery process is another example of a direct 
reduction process. The powdered ore mixed with charcoal 
is heated on the open hearth of a bloomery furnace fed by 
a blast. In the processes just mentioned, and in nearly all 
the direct processes, the fuel used is charcoal. The methods 
as a rule are expensive and can only be followed where fuel 
and labor are cheap and special ores are accessible. 

Eames' Process. Among the most recent methods of 
making bar iron may be mentioned that of Eames, or the 
process of the Carbon Iron Company. In this process the 
iron ore is deoxidized in a reverberatory furnace which 
has a hearth lined with graphite or graphite mixed with 
iron oxide. The iron ore is mixed with coke which has 
been treated with milk of lime (retarded coke) to diminish 
tendency to oxidation, and placed upon the hearth of the 
furnace. The furnace is heated by natural gas, and the 
reduction takes place at a moderate temperature. 



276 INORGANIC CHEMISTRY. 

When the ore is reduced, the spongy metal is worked 
into balls and afterwards rolled into bars ; or it may be 
charged while still hot into a bath of melted pig iron on 
the open hearth of a steel furnace and ultimately con- 
verted into steel. This process has given satisfactory 
results in Pittsburgh and has passed to the commercial 
scale. 

There are many other processes that have succeeded in 
obtaining iron direct from the ore, but the Eames and the 
American bloom ery process are the most important now 
operated in this country. The Eames process has not yet 
been adopted in Europe. 

Properties of Malleable or Wrought Iron. Wrought iron 
manufactured by the above-described processes always con- 
tains carbon, usually some silicon, phosphorus, and sulphur. 
Chemically pure iron has neither the hardness nor the te- 
nacity of the commercial bar iron. Unless the amount of 
sulphur in the iron is very small it produces brittleness 
in the iron when it is hot, called red- shortness. An excess 
of phosphorus produces brittleness at ordinary temperature, 
or cold- shortness. 

The best wrought iron has a fibrous texture, to which 
its tenacity is due. Such iron is very tenacious, ductile, 
and malleable. When the iron during its manufacture 
has not acquired the fibrous texture the strength is much 
less. Its strength is much greater in the direction of than 
across the fibres. It is thought that phosphorus in iron 
tends to cause large crystals, preventing the fibrous 
texture and weakening the iron. The texture of iron is 
believed to have sometimes changed, gradually becoming 
granular and crystalline by frequent or long-continued 
vibration. 

At a red heat wrought iron becomes pasty and can then 
be readily welded and easily fashioned into shape. The 
smith usually sprinkles the heated metal with sand or 



METALLIC ELEMENTS. 277 

borax, to remove the oxide before hammering the surfaces 
to be welded together. The use of wrought iron for 
structural purposes, ship-building, armor plates, bridge 
construction, etc., has now been largely replaced by that 
of steel. 

MANUFACTUKE OF STEEL. 

S^©el contains more carbon than wrought iron and less 
than cast iron. It is made either (1) by carbonizing 
wrought iron, (2) decarbonizing cast iron, or (3) by fusing 
together wrought iron or steel and cast iron in the proper 
proportion. The grades of metal thus produced have not 
received a nomenclature that is universally applicable. 
In general it may be said that the first method produces 
hard steel, especially used for tools and fine cutlery ; 
the second, and third produce mild or softer steels, 
more generally used for structural purposes. These 
general designations will serve for descriptive purposes. 

For making mild steels there are two principal proc- 
esses, the Bessemer and the Open Hearth. 

Bessemer Process. 1. Acid Lining. In this process pig 
iron melted in a cupola furnace or taken direct from the 
blast furnace is run into egg-shaped vessels known as con- 
verters. The converter (Fig. 12) is externally of iron, is 
lined with acidic or siliceous material, and is arranged so 
as to rotate upon trunnions fixed on either side. Below 
the bottom of the converter is a blast-box, and many holes, 
from a quarter inch to an inch and a quarter in diameter, 
extend from the blast-box through the bottom of the con- 
verter. The converter is turned into a horizontal position 
to receive the charge of from five to twelve tons of iron. 
The air-blast is then turned on under a pressure of fifteen 
or twenty pounds, and the converter rotated to an erect 
position. The air passes up through the melted metal. 
The silicon and manganese are first oxidized with marked 



INORGANIC CHEMISTRY. 



increase of temperature in the converter; then the carbon 
is oxidized to carbon monoxide, which bnrns with a long 
flame at the mouth of the converter. Some of the iron is 
also, oxidized during the blow. 

The oxidized silicon combines with the oxides of iron 



n n r\ n n 




n n n n n . 



- -'■■ ' "." ■-'. ■ . . ■ ■ . ' - ' . ' ' ■ ■ ■ v. 




Fig.12. 

and manganese, and rises to the surface of the metal as a 
slag. 

When the carbon flame drops at the mouth of the con- 
Terter it indicates that the operation is complete, that is, 
that the carbon, manganese, and silicon have been removed 
from the iron. 

The metal thus purified is converted into the desired 
quality of steel by the addition of spiegeleisen or ferro- 
manganese to the melted charge just before it is poured. 
The ferro -manganese is a cast iron rich in carbon and man- 
ganese and of well determined composition; the ferro-man- 



METALLIC ELEMENTS. 279 

ganese is always added in a fused state. The metal is 
allowed to stand a few minutes after this addition and then 
poured into ladles and cast into ingots. The addition of 
the ferro-manganese not only gives the required hardness 
to the steel, but the manganese counteracts the tendency 
to red-shortness. 

The above was the original process, and it will be ob- 
served that the converter was lined with siliceous or acidic 
material. It was found that the process could only be ap- 
plied to iron fairly free from phosphorus, for this objection- 
able constituent was but little removed by the operation. 

Bessemer Process. 2. Basic Lining. The mechanical ar- 
rangements and general principles in the basic process are 
exactly the same as in that just described, but the converters 
are lined with lime and magnesia (basic material), and lime 
to the amount of about T | T the charge of iron is put into 
the converter before the metal is run in. The blow is con- 
tinued a little longer than in the original process, and the 
oxidized phosphorus combines with the lime and is removed 
in the slag. By this modification in the original process it 
has become applicable to iron rich in phosphorus. The slag 
produced in the basic process is rich in calcium phosphate 
and is very valuable in agriculture. The basic process now 
finds wide application. 

It will be observed that in the Bessemer process the 
decarbonization and purification of the cast iron is accom- 
plished by the oxygen of the air. 

Open-hearth Steel.* 1. Pig and Scrap Process. This 
process includes all the methods in which steel is made by 
fusing together wrought iron or scrap-steel, or both, with 
pig iron. The proportions of the constituents of the charge 
will vary with their compositions and the nature of the 

* The designations, and in part the descriptions, of methods employed in 
making open-hearth steel were supplied by Capt. Ira MacNutt, U. S. Ordnance 
Inspector at South Bethlehem Steel Works. 



280 INORGANIC CHEMISTRY. 

product desired. Steel or wrought iron scrap of various 
kinds is used in the charge. The components of the charge 
are thoroughly fused and additions of one or the other made, 
until samples taken from the furnace show the desired 
quality. Spiegeleisen is often added to bring the metal to 
the proper composition. 

Open-hearth Steel. 2. Pig and Ore Process. This process 
includes all those methods in which the charge consists of 
pig iron and iron oxide. A decarburization of the pig iron 
is accomplished mainly by the action of the iron oxide ; 
the process is sometimes termed the direct pig process. It 
resembles in principle the original puddling process. In 
this process the pig iron is melted and the appropriate 
quantity of iron oxide introduced into the furnace. By 
thorough stirring the silicon, carbon, etc., are oxidized and 
removed from the iron; the oxidation is accomplished 
mainly by the oxygen of the iron oxide, but in part by the 
oxygen in the flame used for heating. After six or eight 
hours the operation is complete, but the carbon has been 
too much reduced. The required steely character is im- 
parted by the addition of ferro-manganese or spiegeleisen 
in calculated quantity and until the tested samples from 
the furnace show the desired quality. 

In both these open-hearth processes acid and basic lined 
furnaces are employed, depending upon the quality of the 
steel desired and the nature of the charges. 

The open-hearth processes are conducted in some form 
of reverberatory furnace, and regenerative firing is em- 
ployed. By this means the purified iron can be kept per- 
fectly liquid, due to the high temperature attainable. The 
final product is run off into ingots. 

Martin applied Siemens' regenerative principle to the manufacture of 
steel. This application gave rise to what was called the " Siemens-Martin 
process." One of its important early applications consisted in fusing pig 
iron and scrap wrought iron together in the proper proportion to form 



METALLIC ELEMENTS. 281 

steel, so that this particular application was, at one time, widely designated 
as the Siemens- Martin process. 

There have been many variations in the shape and style of the furnaces 
used in making open-hearth steel; also in the materials used in charging 
and in the method of charging. A partial reduction and the melting of a 
portion of the charge is sometimes made before putting it in the open hearth. 
It will not be attempted to mention all the modifications of the open-hearth 
method; the essential principles are embodied above. In this country the 
term Siemens-Martin is now seldom used and is no longer commercially 
descriptive. 

Cementation Steel. Steel from Wrought Iron ; Hard or 
Tool Steel. The process of making steel from wrought iron 
bars by carbonization is known as the cementation process. 
In this process the bar iron, imbedded in charcoal, is sub- 
jected to the prolonged action of a high temperature. For 
this purpose bar iron of the best quality is cut into suitable 
lengths and placed in chests of fire-bricks. The chests are 
about ten or twelve feet long, three to three and one half 
feet wide and deep, and open at the top. 

The charge of each chest consists of from six to eight 
tons of iron. Ground charcoal is spread upon the bottom 
of the chests, and upon this bars of iron are laid in regular 
order, small intervals being left between adjoining bars ; 
the bars are about four inches wide and a little less than 
an inch thick. Charcoal is then added until the open 
spaces are filled and the bars covered by a continuous 
layer ; over this another layer of bars is placed, and the 
operations repeated until the chests are full. A thick layer 
of carbon is placed at the top, and the whole is covered with 
a layer of grinders' waste (wheels-warf, silica, and iron dust 
from the grinder's wheel) or similar material. This sub- 
stance at a moderate heat becomes plastic and forms a per- 
fect cover to the chests and prevents contact of air with 
the charcoal. The chests are generally placed in pairs in a 
dome-shaped furnace, the fireplace being below the chests, 
and the flues passing up between and at the sides, the 



282 



INORGANIC CHEMISTRY. 



whole being provided with appropriate chimneys (Fig. 13). 
The temperature is raised gradually until it is about 2000° 
F., at which point it is maintained for a period of six or 
ten days, the time depending upon the quality of the steel 
required, the harder steel requiring the longer time. The 




Fig. 13. 



progress of the operation is known by the appearance of 
trial bars, one of which is arranged in each chest so that it 
may be withdrawn when desired. When the operation is 
complete the bars are taken out and are found to have in- 
creased from one half to one per cent in weight and are 
usually covered with hollow protuberances resembling 
blisters, hence the term blister steel. Analysis shows that 
the increased weight is due to the combination of carbon 



METALLIC ELEMENTS. 283 

with the iron, and the carbon is found not only at the sur- 
face, but also at the centre of the bars. 

The chemistry of the process is believed to be due to the 
action of carbon monoxide upon the iron. It has been 
shown experimentally that soft iron, at a low red heat, is 
capable of absorbing four times its volume of carbon mon- 
oxide ; the action of the iron upon the gas is thought to be 
indicated by the equation 

Fe x + 2CO = Fe x C + C0 2 ; 

the carbon dioxide produced is reconverted into carbon 
monoxide by the charcoal : 

CO, + C = 2CO. 

The carbon monoxide is produced, in the first instance, 
by the action of the small amount of atmospheric oxygen 
present in the chest upon the carbon. The carbon monox- 
ide absorbed by heated iron is retained unchanged unless 
the temperature of the iron be raised above a red heat. 

Shear Steel. Though carbon is found throughout the 
bars of the above-described steel, it is more abundant 
nearer the surface, while below the surface are found 
numerous blister cavities. To render the steel more homo- 
geneous and improve its quality much of it is subjected to 
a process of fagoting. The bars are broken, piled, heated, 
and forged into shape tinder the tilt-hammer as is the case 
with bar iron. One heating and welding constitutes single- 
shear steel. The density, tenacity, malleability, and duc- 
tility of the steel are greatly increased by fagoting, and 
such steel is suitable for the manufacture of certain kinds 
of tools, woolen shears being among them, hence the name 
shear steel. The fagoting operation repeated upon the 
single-shear steel produces double-shear, the latter again 
being superior to the single-shear for certain purposes. 

Crucible Cast Steel. The best steel for tools and for 



284 INORGANIC CHEMISTRY. 

many other purposes is produced by melting blister steel 
in crucibles, usually of clay or plumbago. 

The blister-bars are broken into fragments and a charge 
of from fifty to one hundred pounds introduced into the 
crucible. The fusion is accomplished in a wind furnace, 
the surface of the metal being protected from oxidation by 
covering it with some fusible silicate or other flux. The 
fused contents of the crucibles are poured into the moulds, 
and when heavy ingots or castings have to be made the 
contents of several crucibles are poured into the same 
mould ; sometimes this is done directly, but in large cast- 
ings the metal is poured from crucibles into a receiver and 
from that into the. mould. The cast steel is more homo- 
geneous than the shear steel and is used to make the finest 
cutlery. 

Crucible steel is, apparently, justly thought better than that from other 
sources (open-hearth and Bessemer). The cost of crucible steel limits its 
production to that of high quality for cutting instruments, for springs, for 
fire-arms, etc. Other material than blister bars is used for the production 
of crucible steel, but even then the product is thought inferior to that from 
the former source. It is often found advantageous, in crucible steel for 
special purposes, to introduce some manganese. Small quantities of chro- 
mium, tungsten, silicon, nickel, and titanium also appear to have beneficial 
effects upon steels requiring special properties. 

Case-hardening . Small objects which require the ex- 
ternal hardness of steel can be made of bar iron and then 
hardened externally by heating them in contact with car- 
bonaceous matter and afterwards cooling suddenly ; this 
process is known as case-hardening. The reverse process 
to this consists in heating articles made of cast iron in con- 
tact with oxide of iron or other suitable oxidizing agent, 
by which they are converted into malleable cast iron. In 
case-hardening carbonization is effected, in the reverse 
process decarburization. 






METALLIC ELEMENTS. 285 

DISTINCTION BETWEEN CAST IRON, STEEL, AND WROUGHT 

IRON. 

Properties of Steel. Some varieties of these metals grade 
imperceptibly into each other. The following distinctions 
afford the best general classifications. Cast iron includes 
all varieties which are non-malleable ; the varieties which 
are malleable and cannot be hardened by sudden cooling are 
wrought iron ; the varieties which are malleable and can be 
hardened by sudden cooling are steel. In English-speaking 
countries the terms mild steel or ingot steel and ingot iron 
are often used synonymously, and, thus used, they include 
all the refined irons except the softest wrought iron and 
the hardest steel — that is, all the refined iron made by the 
processes requiring complete fusion throughout the opera- 
tion. Wrought iron results from refining pig iron by 
fusion, which is not continued throughout the operation. 

Steel is hardened by sudden cooling from a high tem- 
perature, and it is usually done by plunging it into oil or 
water. It is tempered by reheating the previously hard- 
ened steel, but not so highly as before, and cooling more 
or less suddenly. It is annealed by reheating the hardened 
steel and cooling slowly. After the first operation steel is 
hardest and most brittle ; after the third it is softest and 
toughest, and after the second it is in an intermediate 
condition. The foregoing terms are not always used in 
the sense here given. 

The mild steels have nearly entirely replaced bar iron 
in structural works. Steel has also displaced iron in 
armor-plates in war- vessels. The qualities of steel for this 
latter purpose have been greatly improved both by the 
foundry treatment of the large masses and by the addition 
of a small per cent of the other metals ; one, the most 
important alloy, being that with nickel, which is used in 
the celebrated Harvey process. A still better steel for armor- 



286 INORGANIC CHEMISTRY. 

plates has been recently produced, but the treatment and 
composition are kept secret. 

Chemical Properties of Iron. Pure iron is not acted upon 
by dry air at the common temperature. At a red heat it 
oxidizes and will burn at a white heat, in both cases form- 
ing the black oxide. The finely divided metal obtained by 
reducing the red oxide with hydrogen, takes fire sponta- 
neously when exposed to the air. At a red heat iron 
decomposes water with the liberation of hydrogen. 

Pure water at the common temperature does not tarnish 
the surface of iron, but the combined agency of water and 
carbon dioxide produces rusting, which is due to the 
formation of hydrated sesquioxide, 2Fe 2 3 ,3H 2 0. In the 
action the carbonate is first produced and this is dissolved 
by water containing carbonic acid, the dissolved carbonate 
is decomposed by the oxygen of the air and converted into 
the hydrated sesquioxide ; 

(Fe + H 2 + C0 2 = FeC0 3 + H 2 
and 4FeC0 3 + 2 + 3H 2 = 2Fe 2 3 ,3H 2 + 4C0 2 ). 

This reaction explains why the rusting of iron is so greatly 
facilitated by acid vapor. The stains so frequently observed 
to proceed from an iron nail are diffused by the formation 
and solution of the carbonate and subsequent conversion 
of it into the hydrated oxide or other insoluble form ; wet 
linen in contact with a nail is very soon thus stained. 

Dilute sulphuric, nitric, and hydrochloric acids act 
readily upon iron, but the two acids first named have no 
perceptible action when concentrated. 

Iron forms two classes of compounds, the ferrous and 
ferric/, in the first it is a dyad ; in the second it may be 
regarded as a triad or tetrad. 

Iron Oxides. There are three oxides of iron, FeO, Fe 2 3 , 
and Fe 3 4 . 

Iron Monoxide; FeO. This is a powerful base, and readily absorbs 



METALLIC ELEMENTS. 287 

oxygen, passing to Fe 2 3 . It is not found in the free state, but can be 
artificially produced by careful manipulation. 

Sesquioxide of Iron ; Ferric Oxide ; Red Oxide ; Fe 2 9 . 
This oxide is a weak base and is isomorphous with alumina. 
It occurs abundantly in nature as specular iron ore, of 
which there are many varieties. The artificial sesquioxide 
is frequently used as a red pigment, under the name of 
Yenetian red. For this purpose it is prepared by decom- 
posing the ferrous sulphate by heat. The hydrated ses- 
quioxide constitutes the brown hsematite or limo.nite ore. 

The' sesquioxide and its hydroxide are the common color- 
ing matter of the soils. Its presence in the soils favors the 
decomposition of organic matters by supplying oxygen to 
them. In this action the ferric oxide is reduced to the fer- 
rous, this latter then combines with the oxygen of the air 
and reforms the ferric oxide. This operation is continually 
repeated, the ferrous oxide acting as a carrier of oxygen 
from the air to the decomposing body. When the ferric 
oxide is heated to whiteness or in a reducing flame it loses 
oxygen and passes to the tetroxide. 

Triferric Tetroxide ; Magnetic Oxide ; Black Oxide ; 
Fe 3 Oi. This oxide occurs abundantly in nature and is one 
of the chief ores of iron. It is always produced when iron 
is oxidized at a high temperature. It is a very stable 
compound, which fact has led to its use as a covering to 
protect against rust. In the Bower-Barn process the metal 
heated to redness is subjected to the action of steam by 
which it receives a dense film of the oxide. The same re- 
sult is obtained by subjecting the heated metal to the 
action of the carbon dioxide and air. 

Iron Carbonate ; Spathic Ore ; Siderite ; FeC0 3 . The carbo- 
nate occurs abundantly in nature and is a valuable ore of 
iron. It is often associated with the carbonates of calcium, 
magnesium, and manganese, with which it is isomorphous. 
It is often found in natural waters, being soluble in water 



288 INOBGANIG CHEMISTRY. 



containing carbon dioxide. Mineral springs containing the 
carbonate in solution are called chalybeate springs. For 
reasons already explained, these waters usually deposit 
the hydrated oxide when exposed to the air, hence the 
rusty deposit which always occurs about such springs. 

Ferric Sulphide; Iron Pyrites; FeS 2 . This is the most important 
sulphide, and occurs widely and abundantly in nature. It is sometimes 
used as an ore of iron, but more generally as an ore of sulphur. It is gen- 
erally known under the name of pyrite or iron pyrites. There are two 
other sulphides of iron, FeS and Fe 3 S 4 . T^e first is used in the laboratory 
for making hydrogen sulphide, and is itself prepared by heating iron-filings 
and sulphur together. The Fe 3 S« occurs in nature under the name ofjmag- 
netic pyrites. 

Ferrous Sulphate; Copperas; Green Vitriol; FeS0 4 ,Aq. 
Much ferrous sulphate is obtained as a by-product in the 
manufacture of alum. It is made directly in large quan- 
tity by dissolving scrap iron in warm sulphuric acid, evap- 
orating and crystallizing. It is also made by oxidizing the 
burnt pyrites left in the manufacture of sulphuric acid. 

The salt crystallizes in green crystals which are usually 
tinged with a yellowish white, due to the presence of ferric 
sulphate. Ferrous sulphate is largely used in dyeing, tan- 
ning, and in the manufacture of inks, Prussian blue, Vene- 
tian red, and other pigments. It is a great reducing agent, 
and because of this power is used to precipitate gold 
from solution, and will reduce indigo to the soluble con- 
dition. 

There is a number of other sulphates of iron, the most important of 
which is the ferric sulphate, Fe 2 fS0 4 )3. It has been found in nature, and 
can be produced artificially. Solutions of this salt mixed with solutions 
of potassium and ammonium sulphates produce iron alums. 

Other Compounds of Iron. Iron forms two chlorides, ferrous and 
ferric ; the solution of the first is used medicinally, and that of the second 
for disinfecting. It forms two iodides corresponding to the chlorides. It 
also forms ferrous and ferric phosphates and nitrates, and a number of 
other inorganic compounds too numerous and unimportant to be consid- 
ered here. 






METALLIC ELEMENTS. 289 

Reactions of Iron Salts. Ferrous Salts. By the addition 
of caustic alkaline solutions or ammonia, ferrous salts give 
white precipitates, rapidly changing to green and brown. 
Carbonates of potassium, sodium, and ammonium give 
' white precipitates which change to yellowish brown. Hy- 
drogen sulphide gives no precipitate. Ammonium sulphide, 
(NH 4 ) 2 S, precipitates black iron sulphide, soluble in acids. 
Potassium ferricyanide gives a deep-blue precipitate. 

Ferric Salts. These give Prussian blue precipitate with 
potassium ferrocyanide and intense blue-black with infu- 
sion of nutgalls (gallo-tannic acid). 

COBALT. 

Cobalt occurs in nature generally associated with nickel. Its chief ores 
are the arsenide and sulphide. Cobalt is magnetic like iron, and closely 
resembles iron in other properties. The metal has found no application, 
except to a small extent, in plating, as with nickel. This is accomplished 
by the electrolysis of a solution of the double sulphate of cobalt and ammo- 
nium. The deposit is harder, more tenacious, and of greater beauty than 
nickel. It has been termed superior nickel-plating. 

Useful Compounds of Cobalt. Several cobalt compounds are of con- 
siderable importance in the arts, being used to produce permanent and 
brilliant colors. Some of the most important of these are smalt and The- 
nard's blue or ultramarine. 

Smalt. Smalt is a blue pigment very extensively used in the arts. It 
is a potash-glass colored with the oxide of cobalt. It consists of a mixture 
of the silicates of potassium and cobalt, and sometimes other metals. It is 
used in painting on porcelain, in making stained window-glass, in making 
tiles, and as a blue pigment. 

ThenaroVs Blue ; Cobalt Ultramarine. This pigment consists of alu- 
mina colored with the oxide or phosphate of cobalt. It is used both as a 
water- and an oil-color. There is a number of other permanent pigments 
prepared from the compounds of cobalt. 

Cobalt Chloride. This salt is a basis of one of the sympathetic inks. A 
dilute solution of the chloride has a faint rose-color which is not visible on 
paper, but turns blue upon drying, due to loss of water of crystallization ; 
it disappears again upon cooling, due to absorption of atmospheric moisture. 



290 INORGANIC CHEMISTRY. 



NICKEL. 



Mckel resembles iron and cobalt in many of its proper- 
ties. It is malleable and ductile, and next to manganese is 
the hardest of the metals. It is magnetic like iron and 
cobalt, and nearly always occurs in meteoric iron. The 
ores of nickel are found in numerous places throughout 
the world, but are generally very complex, usually being 
associated with a number of other metals. 

Mckel is largely used for coating iron and other bodies 
by electrolysis, a solution of the sulphate being used for 
the purpose. It is made into crucibles and dishes for use 
in the laboratory. It is used for coin and for making vari- 
ous alloys. Alloyed with copier and zinc it forms German 
silver. The alloy of nickel with steel very greatly excels 
the steel in the important qualities required in armor plates. 
Processes have been devised for rolling nickel into thin 
sheets, and these can be welded to iron and steel plates. 
Pure nickel resists the action of the atmosphere and of 
both fresh- and salt-water almost as well as the precious 
metals. 

MANGANESE. 

Manganese is not used in the metallic state. It resembles iron in many 
of its properties, and its ores are often found associated with those of iron. 
It occurs in nature in many forms, but its principal ore is pyrOlusite^ 
MnO a . 

Pyrolusite; Mn0 2 . This oxide is largely used in the preparation of 
chlorine and oxygen, and in the manufacture of glass. It is also the source 
of the other compounds of manganese. 

Other Oxides of Manganese. The higher oxides of manganese are 
acidic, Mn 2 3 and Mn 2 7 . The latter in contact with water produces per- 
manganic acid, H 2 Mn 2 0e. This acid and its alkaline salts are powerful 
oxidizing agents. By virtue of this property potassium permanganate 
finds application in the laboratory and is used as a disinfectant, Condy's 
disinfecting fluid being composed of it. The sodium permanganate gener- 
ally displaces it as a disinfectant, being the cheaper. 



METALLIC ELEMENTS. 291 

Ferro-Manganese ; Spiegeleisen. These bodies are alloys of iron and 
manganese rich in carbon. The first is the richer in manganese. Both 
spiegeleisen and ferromanganese are largely used in the manufacture of 
Bessemer and open-hearth steel. 

CHEOMIUM. 

Chromium in the metallic state finds no useful application. Some of 
its compounds are largely used in the preparation of pigments. It derives 
its name from the Greek word xP&Ma, because of the color of its com- 
pounds. Chromium is generally found in nature as an oxide in combina- 
tion with iron oxide. Its alloys with iron are important. The presence of 
chromium in iron or steel increases the tenacity, hardness, and elasticity, 
and gives finer texture. 

Important Compounds of Chromium. The compounds of chromium 
most used in the arts are chromates; compounds in which the chromium 
oxide takes the part of an acid radical. These chromates are all made di- 
rectly by the oxidation of the chrome iron ore (FeO, Cr 2 3 ). 

Potassium chromate and bichromate are thus made, the latter (K 2 Cr 2 7 ) 
in large quantities; other compounds of chromium are derived from them. 

Potassium bichromate is used in the preparation of nearly all chrome 
pigments, and in the production of a variety of colors in dyeing and calico- 
printing. It is a powerful oxidizing agent, and is used in the manufacture 
of safety-matches, and as a source of oxygen for organic analysis. It is 
readily reduced by organic matter, and is an agent frequently employed in 
testing the purity of water. Mixed with gelatine and exposed to the light, 
it is reduced, and the gelatine rendered insoluble. This fact is taken ad- 
vantage of in photography, and is the basis of the carbon process. 

Lead Chromate ; Chrome Yellow and Orange Chrome. The lead 
chromates constitute two of the most important- chrome colors, chrome 
yellow and orange chrome. Chrome yellow is the normal chromate of lead 
(PbCr0 4 ), and is prepared by bringing together in solution lead acetate 
and potassium chromate. It is largely used in painting and in calico- 
printing. Orange chrome is the basic chromate of lead (PbCr0 4 , PbO), 
and may be obtained by boiling the normal chromate with lime, by which 
a portion of the acid is removed. Stuffs made yellow with the normal 
chromate may be made orange by a bath of lime-water. 

There are many other chrome colors which are of great permanence 
and have many applications. 



292 INORGANIC CHEMISTRY. 



MOLYBDENUM, TUNGSTEN, AND URANIUM. 

The metals molybdenum, tungsten, and uranium are not used in the 
metallic state. Their compounds have been but little studied, and are not 
of great importance. 

Like chromium they all form acid oxides. 

The compounds of molybdenum find no useful application in the arts, 
but some of them are useful as special reagents in the laboratory. 

Tungsten alloyed with steel in small proportions improves its properties 
in several respects, and such alloy is used in the preparation of certain 
tools. Sodium tungstate is used as a mordant, and muslin steeped in a 
solution of this salt will not burn with a flame. Some of the tungstates 
are used to a certain extent in the preparation of pigments. The tungstate 
of calcium has found recent application in forming a fluorescent surface for 
detecting the Koentgen rays. 

The oxides of uranium are valuable for glazing porcelain black- sodium 
uranite is prized for painting and staining glass, under the name of ura- 
nium yellow. 

BISMUTH AND ANTIMONY. 

Bismuth. This metal is found native in small quantities in widely 
separated localities. In the metallic state it is used only for the construction 
of the electric thermopile, being too brittle for other use. Bismuth is 
chiefly used in the form of alloys. It usually confers hardness and fusi- 
bility upon the alloys, and causes them to expand in solidifying. 

Fusible metal is an alloy of two parts of bismuth, one of tin, and one 
of lead. This alloy fuses below 180° C, though the fusing-point of tin, the 
most fusible of the three, is much above this. An alloy of three parts of 
lead and two of bismuth has ten times the hardness and twenty times the 
tenacity of lead. An alloy of lead, tin, and bismuth is largely used for 
the electrotyping process; it is very fusible and takes a fine impression of 
the mould. 

Compounds of Bismuth. The oxide of bismuth (Bi 2 3 ) is used to a 
limited extent for glass and porcelain staining. Bismuth nitrate is largely 
used medicinally, and also as a colorless flux for certain enamels. The 
oxychloride of bismuth is used to a limited extent as a pigment under the 
name of pearl-white. 

Antimony. Antimony, like bismuth, is too brittle for use in the metallic 
state. Its only application as a metal is the construction of thermopiles 
in conjunction with bismuth. Antimony forms valuable alloys. It gener- 






METALLIC ELEMENTS. 293 

ally increases the fusibility, hardness, and brittleness of the metals, and 
confers the property of expanding upon solidification. It is accordingly 
one of the constituents of type-metal, lead being the other. The same 
metals with tin are used for stereotype plates. With nine-tenths tin it 
forms Britannia metal. The number of useful alloys of this metal is large 
Important Compounds of Antimony. Antimony sulphide, Sb 2 S 3 , is used 
in the preparation of safety-matches, and is frequently one of the constit- 
uents of the friction-tube composition used in firing cannon. It gives a 
bluish-white flame with nitre, and is used in pyrotechny. This sulphide 
roasted in air and largely converted into the oxide is used for coloring class 
yellow. The antimony pentasulphide (Sb 2 S 6 ) is used for vulcanising 
rubber. The sulphides of antimony are used as a basis for the production 
of a number of pigments. 

TANTALUM, NIOBIUM, AND VANADIUM. 
These elements are only obtained in the metallic state with difficulty 
Neither the first two, nor any of their compounds, have been put to 
useful application. Vanadium is widely distributed, but occurs in small 
quantities. Some of the vanadic compounds are used in the preparation 
of pigments, of aniline black, and for dyeing leather black. 

TIN; Sn. 

This is a metal of great antiquity. It is mentioned in 
the Bible and was one of the common metals in the time of 
Moses. Numerous bronze implements containing tin have 
been found in the ruins of Nineveh. It is probable but not 
certain that the Phoenicians obtained the tin ore from what 
are now Cornwall and Devon, more than 1000 b.c. Some 
of the early bronzes contained tin and agree closely in com- 
position with statuary bronze of the present time. The 
Romans used the metal for tinning the interior of copper 
vessels just as is done to-day. 

Occurrence and Preparation. Tin has not been found native. 
It occurs in combination as a sulphide and as an oxide. 
The latter (Sn0 2 ) is the ore from which nearly all the metal 
is obtained. The islands of Banca, Malacca, and the British 
Isles produce the greater portion of the tin. 

Tin Reduction. For reduction the best quality of tin ore 
is crushed and washed to remove as much of the gangue as 



294 INORGANIC CHEMISTRY. 

possible. The ore is then mixed with coal and heated, 
usually in a reverberatory furnace, the air being excluded to 
favor the reducing action of the carbon. If the ore is re- 
fractory some flux is added to form a slag. The metal thus 
obtained is cast into blocks which are made purer by a 
second slow fusion, liquation. The purer metal thus ob- 
tained undergoes further treatment in the melted state, be- 
ing well agitated to remove dross and other impurities. 

Properties of Tin. Pure tin is nearly the color of silver. 
It is soft and malleable at ordinary temperatures, and emits 
a crackling sound when bent or twisted. It is the most 
fusible of the common metals (227° C). It is intermediate 
in hardness between lead and zinc. Its specific gravity is 
7.3. Its malleability increases up to 100° C; at this point 
its malleability is only exceeded by gold, silver, and cop- 
per. Heated near to its melting-point it becomes brittle. 
It has little tenacity, is little affected by air and moisture 
at common temperatures, but if kept fused in contact with 
the air it oxidizes rapidly, forming a white powder. It is 
readily soluble in hydrochloric acid with evolution of hy- 
drogen; dilute nitric acid acts upon it with great energy, 
converting it into a white powder. 

According to Bloxam, extreme cold converts tin into a modification 
known as gray tin. The specific gravity of gray tin is only 5.73, and when 
fused it becomes ordinary tin. Spontaneous disintegration of tin may 
occur from great reduction of temperature. 

Uses of Tin. Tinning. Owing to its permanence under 
ordinary influences and its resistance to vegetable acids, 
tin is largely used for coating other metals. The manufac- 
ture of tin-plate absorbs more tin than any other industry. 
Tin-plate, or the material of which articles called tin ordi- 
narily consist, is made by coating iron or very mild steel 
with tin. Steel, which is now most generally used, is first 
carefully annealed. Then the annealed steel or iron plates 
are carefully prepared, so as to present a chemically clean 



METALLIC ELEMENTS. 295 

surface. The cleaned plates are dipped once or twice into 
melted tin. The tin coating protects the iron or steel plate 
so long as the surface is unbroken, but when the iron is 
exposed the two metals form an electric pair and, of the 
two, the iron is the more readily attacked and eaten a way. 
With a zinc coating, under similar circumstances, the zinc 
is attacked. 

Tin-plate is made in large quantities in Europe, and the 
industry has now been introduced into this country. Tin is 
also used to coat the interior of lead or other pipes used by 
brewers, distillers, and others. 

In terne-plate the coating is an alloy of tin and lead. 

Culinary utensils are frequently tinned inside. This 
process is simple, and has been practised for many centu- 
ries. The surface of the utensil to be tinned, which may 
be copper, brass, or iron, is made chemically clean. Some 
tin melted in the vessel is then spread over the surface with 
tow. A skilful workman thus produces a thin uniform 
layer of tin, which greatly increases the wearing power of 
the vessel, and almost imperceptibly adds to 'the weight. 
So slight is the increase of weight that the ancients thought 
that there was none, and Pliny expresses surprise at so 
remarkable a result. 

Tin-foil is largely used, and should be made from the 
best tin. In its manufacture bars of tin are hammered or 
rolled to a certain thickness, then cut up, and the opera- 
tion repeated until the required thickness is attained. 

Alloys. Tin enters into the composition of a large number 
of alloys. It alloys with lead in all proportions, and many 
solders and pewters are composed of these metals, all of 
which melt at temperatures lower than does either constit- 
uent. In applying a solder the surfaces to be joined should 
be chemically clean; borax or sal-ammoniac is generally 
applied to dissolve off any oxide. 

Gun metal and bronze are alloys of copper and tin. 



296 INORGANIC CHEMISTRY. 

Oxides and Salts of Tin. Besides the binoxide of tin (SnO a ) there is 
a monoxide (SnO). Each of these oxides forms a series of salts, the first 
acting as an acid, and the second as a basic oxide. There have been ob- 
tained several other oxides. The stannic oxide by hydration forms two 
important acids, the stannic and the metastannic. These acids form a 
large number of salts, the most important of which is the sodium stannate, 
largely used as a mordant in dyeing and calico printing. 

Tin forms two classes of salts (stannic and stannous) corresponding to 
both hydracids and oxyacids. None of these salts are of great technical 
importance, though some of them are used in dyeing and calico printing. 
Several tin salts of vegetable acids (oxalate, acetate, citrate, and tartrate) 
are similarly used. 

TITANIUM, ZIRCONIUM, THORIUM, GERMANIUM, AND 
CERIUM. 

These metals are among the rare elements and have found no use- 
ful applications. Titanium is remarkable in that it combines directly with 
nitrogen when strongly heated in air. Titanic acid has been employed in 
the manufacture of artificial teeth. The oxide of thorium, together with 
those of cerium and zirconium, is used in the preparation of the mantle of 
the Welsbach burners. The other compounds of these metals are not of 
technical importance and will not be described here. 

LEAD; Pb"; 205.4. 

Occurrence. It is doubtful whether lead has ever been 
found in the native state, but it occurs in a large number 
of natural compounds. The sulphide or galena, PbS, is 
the most abundant and principal ore of lead. The carbon- 
ate and sulphate are met with in certain localities in suffi- 
cient quantity to form important ores. These and other 
compounds of lead, associated with ores of silver and with 
the oxides, sulphides, and arsenides of iron, antimony, and 
other metals, are frequent sources of lead in our Western 
States. 

METALLURGY OF LEAD. 

Until about 1870 substantially all the lead in commerce 
was obtained by working galena or galenite, PbS. This 






METALLIC ELEMENTS. 297 

ore is the form in which most of the lead occurs, but the 
metal itself is now obtained in enormous quantity as a 
by-product in the reduction of silver. In these cases in 
addition to the lead sulphide a number of other bodies are 
generally present, mainly those above mentioned. Lead 
is obtained in silver and gold mining in such large quanti- 
ties that the method of producing the enriched lead or 
base bullion, as it is called, might with equal propriety be 
described along with those metals. 

The method of obtaining the lead from the galena is 
simple in principle and execution when the ore is compara- 
tively pure ; with impure ore the processes increase in 
complexity and number. The processes may be conven- 
iently separated into three : 1st. The method of self- 
reduction ; 2d. The method of roasting, oxidation, and 
subsequent reduction by carbon ; 3d. Reduction by iron. 

First Process. The simplest method of reduction is 
carried out in a reverberatory furnace and is usually termed 
the air -reduction or self -reduction method. In this method 
the galena is roasted at a moderate heat and partially con- 
verted into the oxide and sulphate. The temperature is 
then raised and the unchanged sulphide reacts upon the 
oxide and sulphate, freeing the lead : 

2PbO + PbS =S0 2 + 3Pb 
and PbS + PbS0 4 = 2Pb + 2S0 2 . 

A small quantity of lime is usually added with the ore for 
the purpose of forming a slag with the siliceous matter 
present. This method is applicable to the purer forms of 
galena. The other two methods to be mentioned are appli- 
cable to ores poorer in lead, or associated with other min- 
erals which make their reduction in reverberatory furnaces 
impracticable. 

Second Process. The second method consists in convert- 



298 INORGAJSIC CHEMISTRY. 



ing the galena into the oxide and reducing the oxide with 
carbonaceous matter. 

In this method the ore is first roasted until free or very nearly free from 
sulphur. It is then mixed with fuel and flux (iron oxide and lime) and 
smelted in a blast furnace. The lead is reduced by the carbonaceous 
matter, and the impurities are removed as slag. The first heating in this 
process is generally accomplished in a calciner (a kind of reverberator) 7 
furnace). 

The Third Process. In this process the raw ores are 
treated direct in a blast furnace and the reducing agent is 
iron : 

PbS + Fe = Pb + FeS. 

There is added to the charge, if iron oxide is not already 
present in the ore, metallic iron or more generally rich iron 
slags or iron ore. In the latter cases the iron ores are re- 
duced by the carbonaceous matter of the fuel, and the 
iron decomposes the galena, freeing the lead and forming 
iron sulphide as indicated above. 

The iron sulphide formed combines with some of the lead sulphide and 
other, sulphides present in the ore, and yields a matte which is lighter 
than the lead and easily separated from it. The matte is subjected to 
other treatment for saving the lead, copper, and silver when the latter 
are present. The slags of the first and second processes are often treated 
by the third method. Some lead ores are treated by two of the above 
processes. Galena has also been reduced by iron directly in a reverbera- 
tory furnace. 

American Western Method. The last two processes have 
been substantially combined in one in this country, and it 
has been used extensively for the production of enormous 
quantities of argentiferous lead, notably in Montana, Colo- 
rado, and at Eureka, Nevada. The modified process con- 
sists in treating the raw ore direct in blast furnaces. The 
ores treated are usually of the complex nature already 
mentioned. When sulphur is present in large quantity it 



. 



METALLIC ELEMENTS. 299 

is often advantageous to roast the ores before smelting. 
This roasting is accomplished in large furnaces of the 
reverberatory pattern. If the gangue does not contain the 
necessary ingredients, the ore is mixed with the proper 
material for flux and charged into the furnace with car- 
bonaceous fuel. The charge of the furnace in general 
terms consists of the ore and gangue to which, depending 
upon their composition, is added one or more flaxes, as 
iron ore, siliceous matter, and limestone or dolomite. The 
result of the smelting operation gives three distinct prod- 
ucts, all of which are drawn from the same furnace in the 
liquid state. The lowest is the rich lead called base bullion, 
which is drawn off into pigs, preparatory to refining. The 
second is termed speiss and is principally composed of a 
combination of iron with arsenic and sulphur ; antimony 
and other metals are often present in small quantity. The 
third layer is the slag and consists essentially of the silicate 
of iron. 

The speiss is frequently divisible into two parts, the 
speiss proper and the matte ; the matte is mainly iron sul- 
phide; the speiss proper, iron combined with arsenic and 
antimony. The matte carries more silver than the speiss 
proper and is sometimes worked over. The speiss carries 
more gold when it is present than the matte and some 
silver, but no way of extracting the gold economically has 
been invented. This speiss has been produced in great 
quantities at the western smelting works and contains a 
large amount of gold and silver. 

In the smelting of lead ores considerable quantities of 
lead fume are carried off with the smoke from the furnaces, 
and many processes have been tried for the collection and 
saving of this lead. The method usually adopted is to 
cause the furnace gases to pass through a series of flues 
aggregating several miles in length. The lead fume settles 
very slowly even in quiescent air, which fact explains the 



300 INORGANIC CHEMISTRY. 

great length of the flues. These flues are cleared out 
intervals and much fume is secured. The fume consists of 
lead sulphate, lead oxide, and lead sulphide. 

DESILVERIZING LEAD. 

When lead from any of the above sources contains 
enough silver to make its extraction profitable it is desil- 
verized. The production of the lead at many of the Western 
works is but the first step toward obtaining the accom- 
panying silver, and such lead is always desilverized. The 
silver can be extracted with profit when the lead contains 
one ounce of silver to the ton. 

The desilverizing process involves three distinct opera- 
tions, softening, concentration, and cupellation. The ob- 
ject of the first is to remove base metals which would inter- 
fere with the separation of the silver and lead ; the second 
is to concentrate the silver in a smaller quantity of the 
lead ; the third is to complete the separation of the silver 
from the remaining portion of the lead. 

The operation preliminary to the concentration is soften- 
ing the lead, sometimes in our Western States merely 
termed calcining. The object of softening is to remove from 
the lead, antimony, zinc, copper, arsenic, sulphur, or other 
oxidizable bodies as fully as possible. This removal is ac- 
complished by taking advantage of the difference of fusi- 
bility and difference of oxidizability. The softening is 
effected in a reverberatory furnace. The smelted lead is 
fused at a low temperature, and the copper, being the less 
fusible, can be partially removed as a scum from the lead, 
which fuses first. The heated air plays upon the molten 
metal by which the more oxidizable bodies are converted 
into oxides which are volatilized or float upon the surface 
and are removed. This continually exposes fresh surfaces 
of the metal to the action of the air and facilitates the oxi- 
dation of the impurities. When the impurities are too 






METALLIC ELEMENTS. 301 

abundant for this ordinary treatment, the melted metal is 
agitated by a jet of steam discharged into it which is more 
efficient in exposing the metal to the action of the air. In 
this operation some of the lead is of course oxidized and 
carried off with the other impurities, but these oxidized 
products are all worked [over again to recover the metals 
contained. These products from the softening furnace are 
called crasses, the term slag having very appropriately 
been limited to fusible silicates. 

Parke's Desilverizing Process. After "softening," the 
further concentration of the silver, or the desilverization 
of the base bullion, in this country, is accomplished by 
Parke' s desilverizing process. This process depends upon 
the fact that zinc alloys more readily with silver than with 
lead, and when zinc is melted with argentiferous lead and 
the mixture allowed to cool, the portion which first solidi- 
fies is an alloy of silver, zinc, and lead, containing nearly 
all the silver and only a small amount of lead. The zinc em- 
ployed amounts to about two per cent of the lead treated. 

From the rich alloy of zinc, lead, and silver the zinc is 
separated by distillation and used again. The remaining 
alloy of lead and silver is subjected to cupellation, which 
separates the silver from the lead. The cupellation will be 
described after we have explained the principles of another 
important process for concentration. 

Pattinson's Desilverizing Process. This process depends 
upon the fact that an alloy of lead and silver is more fusible 
than the lead itself. In Pattinson' s process the argentif- 
erous lead is melted and allowed to cool slowly while being 
constantly stirred. Near the melting temperature of the 
lead this metal crystallizes out, carrying only very minute 
quantities of silver; these crystals are continually removed, 
and the lead left behind is very rich in silver. 

A modification of the Pattinson process consists in agi- 
tation of the molten metal by a jet of high-pressure steam ; 



302 INORGANIC CHEMISTRY. 



this facilitates the crystallization of the lead and removes 
more fully copper and antimony; it also saves time and 
labor. In this method the enriched alloy is drawn off in 
the liquid state from the lead. This modified process is 
known as that of Rozan. It was long employed at the 
Richmond mines at Eureka, Nevada, and is not used else- 
where in this country. 

Cupellation. The rich lead obtained by either of the pro- 
cesses just described is then subjected to cupellation or re- 
fining. This operation depends upon the fact that the 
melted lead readily oxidizes in air, while silver does not. 
The rich lead is melted in a cupel on the hearth of a rever- 
beratory furnace. The cupels are about four or five feet 
Long and two or three feet wide and six or seven inches 
deep. They are made of bone-ash and pearl-ash. Over 
the melted surface of the lead a blast of air is made to 
play. The lead is rapidly oxidized, and the blast drives the 
oxide to the mouth of the refinery, where it flows out in the 
liquid state into pots and is removed. As the oxidation 
proceeds more lead is added, and the operation is not gen- 
erally completed in a single cupel. When the silver amounts 
to about one tenth of the contents the concentrate is drawn 
off and the oxidation completed in a second cupel. The 
oxide of lead which is removed carries some silver and is 
always reduced again. The bottoms of the cupels become 
saturated with lead oxide and are broken up and smelted 
in the blast furnace. 

Properties of Lead. Lead is a bluish-gray metal. It is 
so soft as to leave a streak when rubbed on paper. It is 
malleable and ductile, but has little tenacity. Its hardness 
is increased by zinc, antimony, and copper. Its specific 
gravity varies with the conditions under which it is ob- 
tained, but is about 11.3. Its fusing-point is 235° C. It is 
readily oxidized in the presence of moist air and then, in 
the presence of acid vapors, forms salts. The basic carbon. 



. 



METALLIC ELEMENTS. 303 

ate of lead thus often results from the action of the carbon 
dioxide of the air. In a finely divided state lead is pyro- 
phoric. 

The action of water upon lead is influenced by the salts 
dissolved in the water. Nitrites and nitrates increase the 
action of water upon lead, and the sulphates and carbonates 
decrease this action. The fact that lead is a cumulative 
poison, and that water long in contact with it is liable to 
contain some lead, make great care necessary in using waters 
that have been in contact with lead. Water that has been 
standing long in lead pipes or conveyed for long distances 
in such pipes should not be habitually used for drink- 
ing. 

Dilute nitric acid acts readily upon lead, but it resists 
the action of all the other common mineral acids when at 
ordinary temperature ; even hydrofluoric acid does not 
attack it. Hot concentrated hydrochloric and sulphuric 
acids act upon it. 

Uses of Lead. Lead is largely used in the form of sheets, 
water channels, pipes, and in construction work. Its resist- 
ance to the action of acids makes it very useful in sulphuric 
acid works and in many appliances of the chemical labora- 
tory. It finds many uses in the preparation of alloys, type 
metal, pewter, solder, etc. 

It is the metal from which shot are made, and for this 
purpose the molten metal is caused to flow through cullen- 
ders with apertures of proper size and to fall for some dis- 
tance into vessels holding water, A small amount of arsenic 
(two per cent) is always alloyed with the lead in this opera- 
tion. The arsenic makes the lead more fluid, hardens it 
when cool, and increases its tendency to take the spherical 
form in passing through the air. The size of the holes in 
the cullender, which must be smooth and round, the tem- 
perature of the melted lead, and the distance through which 
it falls determine the size of the shot. The height of the 



304 INORGANIC CHEMISTRY. 

tower varies from thirty feet for small to fifty feet for large 
shot. 

Lead pipes are usually made by forcing the melted 
metal through the annular space between a die and a con- 
centric spindle or mandrel, the die fixing the exterior 
diameter of the pipe, and the mandrel the interior. The 
largest amount of lead is consumed in the manufacture of 
white lead. 

Lead Oxides. There are fire oxides of lead known, the 
most important of which are the monoxide and red lead 
(PbO and Pb 3 4 ). 

Lead Monoxide; PbO. This body occasionally occurs 
native. There are two varieties of the artificial product, 
massicot and litharge. Massicot is produced when melted 
lead is heated at a moderate temperature in the air, and is 
a yellow powder. "When the oxidation takes place at a 
temperature sufficiently high to fuse the oxide formed, it 
gives litharge, which is reddish brown in color. Litharge 
readily combines with silica at high temperature and forms 
lead silicate. It is largely used in the manufacture of flint 
glass and in glazing earthenware ; it is also used for the 
production of lead acetate and other lead salts. 

Red Lead ; Min ium ; Pb z O^ Red lead is made by heat- 
ing massicot in air at a temperature not high enough to 
fuse it. It is largely used in the manufacture of flint glass, 
as a cement in steam -joints, as an oxidizing agent in the 
manufacture of matches, and as a pigment. 

White Lead ; Basic Lead Carbonate. The commercial white 
lead is essentially a basic carbonate, which results from the 
combination of the normal carbonate with one or more mole- 
cules of lead hydroxide : 2PbC0 3 ,Pb(OH) 2 . Many meth- 
ods have been invented and tried for the manufacture of 
this important compound. All of these which have been 
commercially successful depend upon the same principle, 
the formation of a basic salt of lead and the decomposition 



METALLIC ELEMENTS. 305 

of this salt by carbon dioxide. The oldest method (the 
Dutch method) and that which still gives the best white 
lead for paints depends upon the formation of a basic 
acetate of lead and the conversion of this into white lead 
by carbon dioxide. In this method thin sheets of metallic 
lead are exposed to the combined action of the vapor of 
acetic acid and carbon dioxide. The lead is gradually con- 
verted into white lead, which has to be separated from the 
metallic lead, ground, and washed. The chemical actions 
which produce the result are, first, the production of a 
normal lead acetate, which combines with the lead hydrox- 
ide to form basic lead acetate. Then the carbon dioxide 
decomposes the basic acetate, forming basic carbonate and 
reproducing the normal acetate. This action is then re- 
peated, the acetic acid a cting as a carrier between the lead 
and the carbon dioxide. A small amount of the acetic 
acid will convert a large amount of lead into the carbonate. 
The above method is also used in England. 

White lead made by this method has retained its superi- 
ority over all others as a pigment. This superiority consists 
in greater covering power, durability, and opacity. These 
properties are believed to be due to the fact that the Dutch 
pigment in its ultimate constitution is less crystalline and 
more nearly amorphous than that from any other source. 

Various efforts have been made to hasten the process for the produc- 
tion of white lead, among which are the German and French methods. In 
the former the actions described are aided by artificial heat, the reagents 
being enclosed in stoves. The French method (Clichy) involves the sepa- 
rate preparation of lead oxide and the action of acetic acid upon it, the 
result being treated with carbon dioxide. This method slightly modified 
is largely used in this country. Another process (Milner's) consists in the 
production of a basic chloride of lead by the action of litharge, common 
salt, and water upon each other, and the subsequent precipitation of the 
chloride with carbon dioxide. The above processes have all to a certain 
extent succeeded commercially ; and while the newer processes are cheaper 
than the Dutch, the product is not as valuable as a pigment. 



306 INORGANIC CHEMISTRY. 

White lead has been produced by several electrolytic processes both in 
this country and abroad. One of recent American origin (Brown process) 
for which very superior claims have been made is as follows : Sodium 
nitrate is decomposed by the electric current between lead and copper 
electrodes. Lead nitrate and sodium hydroxide are thus formed and dis- 
solved at the two electrodes. The solutions are drawn off and mixed in 
the proper proportions, when sodium nitrate is reproduced and lead 
hydroxide precipitated as an amorphous powder. This nitrate may be 
again electrolyzed. A solution of sodium carbonate is added to the lead 
hydroxide by which sodium hydroxide and basic lead carbonate are formed. 
The hydroxide of sodium can again be converted into the carbonate by 
carbon dioxide and used again. The sodium nitrate and carbonate being 
repeatedly used are consumed only in small quantities. The advantages 
of this process are that no free acids are used, that the operation is com- 
plete in a day, and that the process is non-poisoning — the pigment being 
produced in the form of powder and no grinding being necessary. 

Properties and Uses of White Lead. The pigment is a 
heavy white powder. It is poisonous and the separation 
and grinding of the product, in the English-Dutch method, 
often leads to lead poisoning among the operatives. The 
difficulty of avoiding these effects constitutes a grave 
objection to the process. 

The principal use of white lead is for painting. It is 
thought that when white lead is mixed with oil it saponifies 
some of the oil, and that to this fact is partly due its superi- 
ority as a pigment. Lead paints are discolored by hydro- 
gen sulphide from the formation of lead sulphide. Paint- 
ing which has been thus blackened may often be re- 
stored by exposure to light and air, by which the sulphide 
is oxidized to the sulphate. White lead is sometimes 
adulterated with barium sulphate, and certain pigments 
are made by mixing the two in certain proportions. It has 
been proposed to use lead sulphate as a substitute for white 
lead, but none of these products gives as good results as 
the pure pigment. 

Other Compounds of Lead. In addition to the compounds of lead al- 
ready referred to, there is a number of others, none of which is of any 



METALLIC ELEMENTS. 307 

commercial importance, nor of special use in the laboratory. Some of the 
oxychlorides are used to a limited extent as pigments. Pattinson's oxy- 
chloride gives a white pigment. Paris-yellow and Turner's-yellow belong 
to this class of bodies. 

Reaction of Lead Salts. Caustic alkalies give a white precipitate of 
lead hydroxide with soluble lead salts. Alkaline carbonates give white 
precipitate of lead carbonate. Ammonium sulphide and sulphuretted 
hydrogen precipitate black lead sulphide. 

COPPER; Cu"; 63.1. 

Occurrence. Copper occurs abundantly in the native state 
and as a constituent in many natural compounds. Among 
these compounds the principal ores of copper are the oxides, 
carbonates, and various sulphuretted forms. These last 
constitute the most abundant ores of copper; the most im- 
portant of them is the copper pyrites, a double sulphide of 
copper and iron (Cu 2 S, Fe 2 S 3 ), though there are several 
other sulphides of copper. 

These ores of copper, in addition to the gangue, are very 
frequently associated with the sulphides and arsenides of 
other metals, as iron, antimony, lead, zinc, and silver; gold 
is also often present. 

Copper Reduction. Copper is obtained from its ores by 
two processes usually termed the wet and dry, the latter 
involving fusion and the former not. The method involv- 
ing fusion is the more important industrially. The object 
of the reduction in all cases is of course to separate the 
copper from the impurities present. 

In the United States the great bulk of the copper is 
obtained from three localities, from the region of Lake 
Superior, from Montana, and from Arizona. In the Lake 
Superior region the copper is mainly in the native form, in 
Montana the sulphuretted compounds exist, and in Arizona 
the oxidized forms abound together with the sulphides. 
The dry method or the method of fusion is employed in all 
these localities. 



308 IXORGANIC CHEMISTRY. 

Dry Reduction. 1. Concentration of Native Copper ; 
Lake Superior. Although there have been found immense 
masses of native copper in these mines varying from forty 
to four hundred tons, these large masses have not been the 
principal sources of the metal. The bulk of the copper of 
these mines is distributed in fine grains through the gangue 
stone, which is either amygdaloid or conglomerate rock. 
The rock is crushed by steam stamps and the metal is sep- 
arated from the gangue by washing. The crushed ore in 
its descent over a series of cradles, which are continually 
jigged or given a jerky motion, is subjected to the action 
of running water. By this means the metal which is heavier, 
collects below the sand, the larger grains nearer the stamps, 
the movable earthy matter being carried along by the 
water. At the lower end of the incline the finer sediment 
is subjected to special treatment on sluice-tables or buddlers 
to collect the very finely divided copper. 

The gangue remaining with the copper is separated by 
fusion with a little flux in a reverberatory furnace and 
copper of great purity obtained. The ores from which the 
copper is obtained vary in richness from .6 to 3 per cent of 
metal. The method of obtaining the copper from the ore 
at Lake Superior is so simple that it is usually termed 
mechanical concentration, but since the product is fused 
and refined it is here included under dry reduction. 

Dry Reduction. 2. Reduction of Oxidized Copper Ores. 
In the Arizona mines a large part of the ores worked up to 
the present time have been oxidized forms. These are re- 
duced in blast furnaces, coke being generally the fuel em- 
ployed. The purity of the oxidized ores (oxides and car- 
bonates) frequently permits the prod action of a high grade 
of copper by the single operation of smelting in the blast 
furnace with carbonaceous matter as reducing agent. The 
Arizona copper ranks next to the Lake Superior in purity. 
In these mines the proportion of the oxidized ores decreases, 



METALLIC ELEMENTS. 309 

and of the sulphuretted ores increases, as the depth in- 
creases. The reduction of the sulphides depends upon the 
principles to be described. 

Dry Reduction. 3. Reduction of Copper Sulphides. The 
sulphuretted ores of copper are those most largely em- 
ployed throughout the world for obtaining this metal, 
These ores are extensively worked in the Western mines in 
this country. The sulphuretted ores are becoming more and 
more important at the Arizona mines, and considerable 
copper now comes from the copper-bearing silver and lead 
ores of Colorado. 

In the reduction of the sulphides, use is made of the 
principle that copper sulphide is less easily reduced than 
the other metallic sulphides present in the ore ; of these 
iron is the most important. 

The older process of reduction consists of a series of 
roastings (heating in air) and fusions of the ore, the number 
of operations varying with the nature and quality of the 
ore. The object of the roasting is to expel arsenic, some of 
the sulphur and antimony, and to oxidize the iron. After 
the first roasting the ore is fused with the proper flux to 
form a slag with the gangue and iron oxide. In this opera- 
tion the gangue and some of the iron are removed and 
coarse metal or a matte is obtained. The matte is essen- 
tially a double sulphide of copper and iron, with greatly 
reduced quantities of antimony and arsenic. This matte is 
then broken up and the operation of roasting and fusion is 
again repeated by which white metal is obtained ; this is 
copper sulphide, nearly free from iron and other base 
metals. The white metal has to be again fused in an oxidiz- 
ing atmosphere by which self-reduction takes place, 

Cu 2 S + 2CuO = Cu 4 + S0 2 , 

and " blister" copper is obtained; or the oxidizing action 
may be continued until all the sulphur is expelled and the 



310 INORGANIC CHEMISTRY. 

copper oxide formed reduced by carbonaceous matter. 
The blister copper has then to be refined, to remove any 
remaining sulphur and the small quantities of the baser 
metals still left. During all the operations sulphur, arsenic, 
and antimony are gradually eliminated. The roasting of 
the ores and matte may be accomplished in heaps, stalls 
(which are rectangular open brick enclosures), reverberatory 
furnaces, or roasting cylinders. The fusion of the roasted 
products is accomplished in reverberatory furnaces or 
shaft furnaces. 

It will be observed that the above method consists of a series of roast- 
ings in which the oxidizable impurities are oxidized together with some of 
the copper. These are followed by smelting operations by which the iron 
is removed as a slag and the copper is deoxidized by some of the remaining 
sulphur. It would be impracticable here to describe in detail all the steps 
in the smelting of sulphuretted ores. The charges of one operation are 
often treated with fresh ore, or with the products of another operation, 
the object in all cases being the removal of the base impurities present 
with the least possible expenditure of fuel and loss of copper. The stability 
of the copper sulphide and the easy reduction of the copper oxide, as com- 
pared to the similar compounds of other elements present, are the basis of 
the method pursued. The operations are sometimes more and sometimes 
less numerous than above indicated, depending upon the nature of the ores 
and the necessity for economy in working. 

Bessemerizing Copper Matte. In this country since the 
year 1890 the practice of bessemerizing the copper matte 
has become very general. In this operation the principle 
of the Bessemer steel converter is applied to the purifica- 
tion of the copper matte (sulphide of iron and copper). The 
matte in the liquid state is run into the converter and the 
blast of air turned on. The liquid condition of the contents 
is kept up by the heat resulting from the combustion of 
the iron and sulphur by the oxygen of the air. The iron 
oxide forms a slag with the siliceous lining of the converter 
and is thus removed ; the sulphur is oxidized and passes off 
as sulphur dioxide. In this country it is usual to pass 






METALLIC ELEMENTS. 311 

from the matte to blister copper by a single blowing, the 
blow being stopped once or twice to draw or skim off the 
slag. In accomplishing this result the matte must contain 
about 50 per cent of copper. The charge for the converter 
may be obtained either by remelting in a cupola furnace, 
the matte obtained in the first operation of smelting, or by 
running the matte directly from the reducing furnaces to 
the converter. In the smelter at Great Falls, Montana, the 
latter plan is in operation. There, the converters are 
directly in front of the furnaces, and the general arrange- 
ments are similar to those of a Bessemer steel plant. 

Under the conditions of our Western copper mines the 
savings of fuel, labor, etc., by the Bessemer modification 
have caused a very extensive application of it. 

Pyritic Smelting without Fuel. An attempt, which has met with 
some success, has been made in this country to extend the principle of the 
converter t© the direct reduction of the native ores in blast furnaces without 
the use of any carbonaceous fuel. In this process it is aimed to oxidize 
the impurities of the ore, and to develop the necessary heat by the oxida- 
tion to remove the impurities themselves and obtain the metal by a single 
operation in the blast furnaces. The blast furnace is thus made to play 
the part of a huge Bessemer converter. 

Pyritic smelting by the heat resulting almost entirely from the oxida- 
tion of the ores employed has been successfully accomplished, but it has 
not been sufficiently developed to determine its probable importance. The 
term pyritic smelting has been in use a long time, and the process just 
mentioned under this heading differs from previous ones employed, in that 
the pyritic ores are required to supply the fuel for their own reduction, to 
act as a menstruum for collecting the precious metal, and as a factor in slag 
production. In the older pyritic reduction the sulphuretted material was 
merely used as a collector of the precious metals and not for the second 
and third purposes. 

Copper Reduction by the Wet Method. This method de- 
pends upon the conversion of the copper in the ores into a 
soluble form and the precipitation of the copper from solu- 
tion. The method is in general applied to the ores that are 



312 INORGANIC CHEMISTRY. 

very refractory or are poor in copper. The copper salts 
commonly produced are the chlorides and sulphates. The 
copper oxides or sulphides may be converted into chlorides 
by roasting with common salt, or treating the ore with a 
solution of ferric chloride or hydrochloric acid containing 
common salt. The sulphide ores may be converted into 
sulphate by carefully roasting or by exposure to air and 
moisture ; such change often occurs in the natural ore 
beds. The oxidized ores may be converted into sulphates 
by the direct action of sulphuric acid or by roasting with 
iron sulphate. 

Metallic iron added to the solution of the sulphate or 
chloride precipitates the copper in metallic condition. The 
precipitated copper has to be melted and refined. 

Electrolytic Refining of Copper and the Extraction of Silver 
and Gold. In the smelting of copper by fusion as above 
described, any gold or silver that is present in the ore is 
retained by the copper. In much of the copper produced it 
is commercially profitable to extract these precious metals. 
Nearly all the copper obtained from Colorado, Montana 
and Arizona, and a large and increasing proportion of 
that from the Lake region is now refined to secure one 
or both of these metals. This is accomplished by elec- 
trolysis. 

For this purpose the copper is cast into plates about 
three inches thick weighing 275 or 300 pounds. These 
plates are made the anodes in decomposing cells, the ka- 
thodes being thin sheets of copper, themselves formed 
especially for this purpose by electrolysis. The electro- 
lyte employed is the sulphate of copper in solution. Under 
the influence of a powerful electric current the anode plates 
are rapidly transferred to the kathodes, while the gold 
and silver fall as slimes in the vats. The kathode plate 
being of electrolytic copper, the entire mass of metal at 
that plate is deposited copper. This process gives copper 



METALLIC ELEMENTS. 313 

of a high degree of purity, but it is not equal to the native 
copper of Lake Superior. 

The deposited copper has to be subjected to fusion to 
destroy its crystalline texture before it is fit for industrial 
purjjoses. The slimes are subjected to the action of dilute 
sulphuric acid, by which the copper is dissolved out ; the 
residue is fused, and the gold and silver separated either by 
electrolysis or by dissolving the silver out with sulphuric 
acid. The silver sulphate is reduced by metallic copper or 
iron. 

Separation of Silver from Copper Matte; Ziervogel Method. This 
method depends upon the fact that by carefully roasting the argentiferous 
copper matte (sulphides of copper, silver, iron, and gold) the silver may be 
left as a sulphate, while the iron and copper are converted into oxides, 
their sulphides being first formed and then decomposed. The sulphide of 
silver can then be dissolved out from the two oxides. The silver is pre- 
cipitated from the solution by metallic copper. 

2. Liquation Process. The crude copper before refining is sometimes 
subjected to the liquation process for the separation of the silver. In this 
process the argentiferous copper is fused with about three times its weight 
of lead. The lead alloyed with the silver is much more fusible than the 
copper, and by careful cooling, this rich alloy may be nearly entirely sepa- 
rated from the copper. The silver is then separated from the lead by 
cupellation. 

Properties of Copper. Copper is a valuable metal in the 
arts. Its specific gravity is about 8.9, a little lower than 
iron. It is very malleable, ductile, and tenacious. Among 
the common metals it is next to gold and silver in mallea- 
bility, and next to iron in tenacity. It fuses at a lower 
temperature than iron. It is one of the best conductors of 
heat and electricity. Its ductility, malleability, and con- 
ductivity are greatly diminished by even minute quantities 
of impurities. Copper is only slowly affected by exposure 
to dry air at common temperature. In the presence of the 
moisture and carbon dioxide of the air, it becomes covered 



314 INORGANIC CHEMISTRY. 

with a green carbonate commonly but improperly called 
verdigris. 

Dilute hydrochloric and sulphuric acids do not act upon 
copper if air be excluded. Hot sulphuric acid acts readily 
upon it. Nitric acid in any form acts upon it, though the 
presence of nitrous acid is said to be necessary to begin the 
action. 

Uses of Copper. Copper is used very extensively, the 
most important use being in the construction of electrical 
machinery and apparatus, for the manufacture of boilers, 
chemical stills and apparatus, kitchen utensils, cartridge- 
cases, and as sheathing for vessels. In sea water the copper 
is corroded, due to the formation of the oxychloride. 
This roughens the surface and gives points of attachment 
for barnacles and other salt water forms, which often 
greatly impede the sailing power of vessels, many tons of 
these animals having been removed from a single vessel. 
Numerous attempts have been made to protect this sheath- 
ing from corrosion. 

Cooking utensils of copper should always be kept per- 
fectly bright to avoid the formation of poisonous salts by 
the acids of food. Even then the joint action of the air and 
the vegetable and other acids often present may contami- 
nate the food. This fact justifies the custom of coating the 
interior of such vessels with tin. Copper is also used in 
making electrotypes and as a constituent of many useful 
alloys. Bronze is composed of copper and tin ; brass of 
copper and zinc. 

Compounds of Copper. The Oxides. Among the compounds 
of copper employed otherwise than as ores may be men- 
tioned the black and red oxides (CuO and Cu 2 0). The first 
is employed as a source of oxygen in organic analysis ; the 
second is used in glass-making, to impart a red color. 

Copper Sulphate. Copper sulphate may be prepared by 
dissolving copper in sulphuric acid, or by the oxidation of 



METALLIC ELEMENTS. 315 

copper pyrites. It is very largely employed in solution, in 
forming electrotypes, and in galvanic batteries. It is also 
largely employed in dyeing, calico-printing, and in the 
manufacture of pigments. 

Carbonates of Copper. The native carbonates of copper, 
when found in massive forms, yield the minerals known as 
azurite and malachite, used in ornamental work. They are 
also used as pigments. 

Some of the other compounds of copper find limited application. The 
hydroxide dissolved in ammonia, known as Schweitzer's reagent, yields 
a solution which dissolves cellulose. The cupric chloride finds some appli- 
cation in calico-printing and in the manufacture of colors. 

Silver; Ag'; 107.1. 

Occurrence. Silver is a pretty widely diffused metal, 
though it occurs only in small quantities. It is found in 
the metallic state. Its principal ores are the sulphide, the 
sulphide in common with the sulphides of arsenic and anti- 
mony, the chloride, the iodide, and the bromide. All these 
are very generally associated with the sulphides of iron, 
lead, and copper. The sulphide is the ore yielding the 
most silver. 



REDUCTION OF SILVER FROM ITS ORES. 

Silver being one of the precious metals, and its ores 
differing in composition and being generally associated 
with a large per cent of other material, its metallurgy is 
not simple. The processes for obtaining the metal may be 
classed under three heads : 1st. Smelting; 2d. Amalgama- 
tion; 3d. Leaching. 

Smelting for Silver. This process is applicable to the ores 
of silver which accompany the ores of lead and copper, 
these last named compounds being present in sufficient 
quantity to render their extraction possible and profitable 



316 INORGANIC CHEMISTRY. 

by smelting. The success of the process depends upon the 
fact that in the operation of smelting and separating the 
lead and copper from the baser matter of the ore the silver 
remains with the lead or copper. It may be said that when 
the silver ores are smelted with the ores of lead and copper, 
the silver ore is reduced with the ores of these metals and 
the silver dissolved and carried down by them. The smelt- 
ing of silver ores associated with lead and copper ores is 
conducted on a large scale in this country. The manner of 
reducing the lead and copper ores has been given, and the 
methods of refining these metals for obtaining the silver 
have been described. These processes, therefore, include 
silver smelting. From the lead and copper ores of Colo- 
rado, and from the copper ores of Arizona and Montana, 
there is a large yield of silver. 

Amalgamation Process. This process depends upon the 
fact that mercury will reduce certain compounds of silver, 
and that it dissolves or amalgamates metallic silver. The 
method is applied to a great variety of ores which, from 
their mineral associates or lack of fuel, cannot be economi- 
cally smelted. The process is an old one, and many slight 
variations in the details of the process exist. The method 
most generally adopted in this country is known as the 
Washoe or pan process; it has been, and is still, largely 
employed in the West. 

If the silver exists in the ores in such form that they 
are readily amalgamated, the process is largely one of me- 
chanical detail. Such ores are in this country termed free 
milling, and the steps in the process are as follows : The 
ore is first crushed in a mortar by stamps. The stamping 
involves the principle of the pestle and mortar; there are 
usually four or more stamps in operation in each mortar. 

In California a single mortar with its stamps is called a 
battery (Fig. 14). In the sides of the mortar are placed 
screens with the proper number of meshes, and when the 






METALLIC ELEMENTS. 



317 



ore is sufficiently crushed it is carried through these screens 
by a stream of water flowing through the mortars. The 
mud from the mortars is charged into iron pans, ground to 
a fine pulp and amalgamated with mercury. The charges 




Fig. 14. 



from the amalgamating pans are passed into tanks in which 
the mercury and amalgam are separated from earthy mat- 
ters. The free mercury is then separated from the amal- 
gam by straining, and the latter subjected to distillation, 
when the mercury passes off and the silver is left behind. 
The mercury is of course collected for future use. The direct 
process is especially applicable to ores rich in native silver, 
silver chloride, and not an excess of silver sulphide. 

Sometimes the ores rich in the sulphide are subjected to 
preliminary treatment before amalgamation. They are 
crushed and roasted with common salt, by which they are 
converted into the chloride. The amalgamation then takes 
place directly, the mercury reduces the silver chloride, and 
the reduced silver combines with another portion of the 



318 INORGANIC CHEMISTRY. 

mercury. The amalgamation is frequently accomplished in 
barrels : 

AgCl + 2Hg = HgCl + AgHg. 

This method was employed with certain ores of the Corn- 
stock Lode rich in silver sulphide, and was formerly em- 
ployed at other places, but it is not now much used in this 
country.* 

The ores from the great Comstock Lode of Nevada were mainly reduced 
by the pan process. The mechanical appliances in such works are gener- 
ally very extensive and consist of (1) the crusher, (2) the stamps, (3) pans 
for grinding and amalgamating, (4) settlers for removing the settlings and 
amalgams from the pulp, (5) the agitators which are supplementary to 
the settlers, (6) appliances for saving slimes and tailings, (7) retorts for sub- 
limation. The crusher breaks the ore when necessary into lumps. The 
stamps are heavy iron pestles lifted and dropped by machinery in iron 
mortars, where the lump-ore is crushed. A stream of water flows through 
the mortar and carries with it the pulverized ore. This water flows into 
tanks, where it deposits the bulk of the earthy matter. The water flowing 
from the tanks always carries certain very fine material which is subse- 
quently collected under the name of slimes. From the tanks the crushed 
ore is conveyed to pans for grinding and amalgamation. These pans are 
generally iron tubs about three feet deep and from four to six feet in diam- 
eter. They are arranged to grind the sand very fine and to thoroughly 
mix it with the mercury, the grinding taking place mainly before the addi- 
tion of the mercury. The settlers are tubs of iron or of wood with iron 
bottoms. In the settlers the pulp is diluted with water and the whole 
agitated to separate the mercury and the amalgam. The separation is 
still further accomplished in the agitators. The amalgam and mercury 
thus obtained are thoroughly washed, strained through canvas to separate 
them, and the amalgam distilled. The earthy matter from the settlers and 
agitators is called tailings; both the slimes and tailings contain some silver 
and are sometimes subjected (the former always) to a second treatment. 
The above description gives the principal steps in the reduction of free- 

* In the old Freiburg method the roasted silver ore is agitated with scrap 
iron and mercury in barrels. The iron assists in reducing the silver chloride, 
and the silver then combines with the mercury. The amalgam is retorted to 
separate the mercury from the silver. 



METALLIC ELEMENTS. 



319 



milling ores; in all such operations in the West there is a common practice 
of adding certain chemicals to the charge in the pan. The so-called chem- 
icals are sodium chloride and copper sulphate. The action of these chemi- 
cals is uncertain, and by some good authorities their beneficial effect is 
doubted. It is thought most likely to be represented by the following re- 
actions: 

2NaCl + CuSO< = NasSO, + CuCl a ; 2CuCl a + Ag a S = 2AgCl + 2CuCl +S; 
2CuCl + Ag 2 S = 2AgCl + Cu a S; AgCl + 2Hg = AgHg + HgCl. 

When the ore is stamped without preliminary treatment 
it is known as wet stamping. In wet- stamping the crushed 
ore is carried from the mortars through the screen by run- 
ning water. When the ores are subjected to a preliminary 
drying or heating the process then involves dry stamping. 
In the dry stamping the crushed ore is driven through the 
screens by the impulse communicated by the stamps. In 
this case, the front of the screen is enclosed by dust-tight 
boxes and special arrangements are made for removing the 




Fig. 15. 

crushed ore from the boxes. The term "drying" refers 
merely to the removal of moisture, "roasting" involves a 
chemical change. The roasting of silver ores is usually 
for the conversion of the ores into chlorides and is gener- 
ally effected in some form of mechanical furnace. 



320 INORGANIC CHEMISTRY. 

There are two types of these furnaces, the horizontal rotating and the 
vertical shaft. The Bruckner revolving cylinder (Fig. 15) may be taken as 
an illustration of the first. This cylinder is from twelve to sixteen feet 
long and five to seven feet in diameter, composed of iron shells;' the whole 
is lined with brick. Passing through the cylinder, from side to side, is a 
number of pipes which form a sort of diaphragm. One end of the cylinder 
fits into a fire-box, and the other into a chimney. The flame from the fire- 
box is made to play through the cylinder. The cylinder revolves about its 
longer axis, and the motion, in connection with the diaphragm, keeps the 
ore properly exposed to the action of the fire. 

The vertical furnace is a small shaft furnace surmounted by a charging 
apparatus which is operated mechanically and which feeds the ore to the 
furnace with the greatest regularity, and exactly as demanded. The Slede- 
felt is the commonly used furnace of this type. 

Leaching Process. This process is applicable to ores of 
silver which either from their nature or motives of economy 
cannot be treated by smelting or amalgamation. It is 
generally practised npon poor, or what are called from the 
difficulty of working them by other methods, rebellious 
ores. It depends upon the fact that certain silver com- 
pounds can, by difference of solubility, be separated from 
accompanying minerals and then the silver obtained by 
simple treatment. The method usually followed in this 
country (Von Patera' s) is to roast the stamped silver ore, 
generally silver sulphide, with common salt, by which the 
ore is converted into the chloride. The roasted ore is 
then leached with water to dissolve out such substances as 
are soluble in that liquid. It is then leached with some 
solvent, generally sodium or calcium hyposulphite, which 
dissolves the chloride. The silver may then be precipitated 
as silver sulphide, by adding calcium or sodium sulphide. 
The silver sulphide is then roasted, lead usually added, and 
the whole cupelled. 

In this process the ore is first dried, crushed by dry 
stamping or rollers, and then roasted with sodium chloride. 

The roasting is done in the Bruckner cylinder already described. Mr. 
Russell has modified the process by leaching the lixiviated product a second 



METALLIC ELEMENTS. 321 

time with a mixture of sodium and copper hyposulphite (made by adding 
copper sulphite to sodium sulphite). The second leaching dissolves out 
native silver and the sulphide of silver. To this solution he adds a solu- 
tion of sodium carbonate which precipitates the lead salts as lead carbon- 
ate; the lead salts may be thus separated. The subsequent operations are 
as described in the Von Patera process. The Russell process is applicable 
to ores and tailings containing the native metal, the sulphide, and greater 
quantities of the baser metals than can be satisfactorily worked by the Von 
Patera process. 

The Ziervogel process of separating silver from copper matte (described 
under Copper) involves the leaching of the silver sulphate from a matte 
prepared by fusion. It therefore is not here included under the leaching 
process, though it is sometimes so classed. 

Properties of Silver. Silver has been known from remote 
antiquity. Its general appearance is familiar to every one. 
It is slightly harder than gold and softer than copper. 
Its specific gravity varies slightly with mode of preparation, 
but is about 10.5. Next to gold it is the most malleable 
metal. It is very ductile ; one grain may be drawn into a 
wire 400 feet long. It contracts in solidifying from the 
molten state. It is the best conductor of heat and electric- 
ity. It fuses at about 950° C. and can be distilled without 
difficulty. Molten silver absorbs over twenty times its 
volume of oxygen, which is given off, with the exception of 
seven tenths of one volume, on cooling. 

It is not oxidized in the air, dry or moist, at any tem- 
perature, though it is oxidized by ozone. It is tarnished 
by hydrogen sulphide in the presence of air with the pro- 
duction of silver sulphide. Pure hydrogen sulphide does 
not attack silver. This tarnish is readily removed by 
potassium cyanide. It is readily acted upon by nitric acid 
with the production of silver nitrate. Hot concentrated 
sulphuric acid acts upon it with the formation of the sul- 
phate. Boiling hydrochloric acid acts upon it. It resists 
the action of fused alkaline hydroxides better than plat- 
inum and is consequently more frequently used in the 
laboratory for crucibles, dishes, etc. 



322 INORGANIC CHEMISTRY. 

Uses of Silver. The principal uses of silver are for coin, 
jewelry, making alloys, and for silvering other metals. 
The standard coin of the United States is composed of nine 
tenths silver and one tenth copper ; for all other useful 
purposes it is similarly hardened. The plating of articles 
may be accomplished by electrolysis, or silver-leaf may be 
charged upon the properly prepared plate by burnishing. 
Silvering may also be accomplished by treating with an 
amalgam of silver, then heating to separate the mercury. 
The chloride of silver with certain reducing salts is likewise 
used to yield a film of silver. 

Frosted silver is prepared from standard silver by heat- 
ing to oxidize the copper, then dissolving out the oxide 
by dilute sulphuric acid ; this gives a surface of nearly pure 
silver and with a blanched, frosted appearance. 

The so-called oxidized silver is produced by immersing 
silver in a solution made by boiling sulphur in a solution 
of caustic potash. It is really the sulphide of silver. 

Pure silver may be obtained from the standard silver by dissolving the 
piece in nitric acid and precipitating the silver from the solution in the 
form of the chloride by the addition of a soluble chloride. The silver chlo- 
ride may then be washed until all the copper salt is removed and heated 
with sodium carbonate : 

2AgCl + Na 2 C0 3 = Ag 2 + 2NaCl + O + C0 2 . 

Compounds of Silver; AgN0 3 . In addition to the ores of 
silver already mentioned, there is a large number of com- 
pounds, the most important of which is the nitrate. The 
nitrate is prepared by dissolving silver in nitric acid, evapo- 
rating to crystallization and then fusing to expel free acid. 
It is used as a cautery in surgery, and for this purpose it is 
usually cast into small cylindrical sticks. Its caustic prop- 
erties depend upon the facility with which it gives up its 
oxygen. It readily yields its oxygen to organic matter 
with the deposition of black metallic silver. There is 



METALLIC ELEMENTS. 323 

nearly always sufficient organic matter in the air to cause 
the nitrate to blacken after exposure for a short time. 
This property accounts for the use of the nitrate for mark- 
ing ink and as a constituent of certain hair dyes. The 
nitrate is the essential constituent of common indelible ink. 
The permanent marking is due to the deposit of the finely 
divided silver in the fibre of the cloth. The nitrate is very 
largely used in the preparation of photographic plates. 
Stains upon the skin from the nitrate may be removed by 
solution of potassium cyanide or tincture of iodine. 

Silver Chloride; AgCl. This compound is always pro- 
duced and precipitated when a soluble salt of silver meets 
a soluble chloride in solution. The precipitate is at first 
white, then violet, and then black. The blackening is 
hastened by the action of sunlight or the presence of 
organic matter. The change of color is due to the conver- 
sion of the chloride into the subchloride. The chloride is 
readily soluble in ammonia or in potassium cyanide. The 
chloride is generally the form to which the silver is brought 
for extraction from the ores by leaching, and in some of the 
amalgamation processes. 

Reactions of Silver Salts. A silver salt in solution yields 
a white curdy precipitate of silver chloride whenever a 
soluble chloride is added. The precipitate is insoluble in 
nitric acid, blackens by exposure to light, and is soluble in 
solution of ammonia. Solutions of silver salts are reduced 
to the metallic state by iron, copper, zinc, and other baser 
metals. 

MERCURY ; Hg. 

Occurrence. Mercury occurs in small quantities in the 
metallic state, but the principal ore and source of mercury 
is the natural sulphide, cinnabar, HgS. The metallic mer- 
cury is disseminated in minute globules through the cin- 
nabar. The chief mercury mines are those of Idria in 



324 INORGANIC CHEMISTRY. 

Austria, Almaden in Spain, New Almaden in California, 
and other mines near San Francisco. 

METALLURGY OF MERCURY. 

The principle of the extraction of the mercury from the 
sulphide is simple. It involves the removal of the sulphur 
and volatilization and condensation of the mercury. To ac- 
complish this result most economically, on a commercial 
scale, an extensive plant is required. 

Only two methods have been employed in the reduction : 
1st. The oxidation and removal of the sulphur of the ore by 
ignition in the air : 

HgS + 2 = Hg+S0 2 . 

2d. By heating the ore with some base, as lime or iron 
scales, by which the sulphur is removed mainly as the sul- 
phide of lime or iron. The second method is seldom em- 
ployed and will not be described. 

Roasting. The metal is now generally extracted from the 
sulphide by roasting the ore in shaft furnaces, the opera- 
tion being a continuous one. The spent ore is removed at 
the bottom and fresh ore fed in at the top of the furnace. 
The air for the oxidation of the sulphur is frequently 
heated before admission to the furnace. For this purpose 
the heat given out in the condensing chambers is most gen- 
erally employed, the air being led through these chambers 
in pipes. During the roasting, the sulphur is converted into 
sulphur dioxide and the mercury volatilized; all the im- 
portant roasting furnaces in this country are shaft furnaces. 
Those which depart from the vertical shaft form consist of 
a series of parallel inclined channels built upon a natural 
slope. The channels take the place of the shaft. The ore 
is fed in at the top, and the fireplace is at the bottom. 

Condensation. With the modern American continuous 
roasting furnaces, the sulphur dioxide, the volatilized mer- 



METALLIC ELEMENTS. 325 

cury, and other products from the furnace are conducted 
into a series of condensers, so extended as to cause the con- 
densation of all the mercury before the products are per- 
mitted to escape into the air. These condensers consist of 
a series of chambers so connected that the vapors from the 
furnace shall pass through them all, the mercury being 
condensed and retained in the chambers. The chambers 
are so constructed that the mercury is gradually brought 
together by virtue of its fluidity, and is removed from the 
chambers at necessary intervals. The chambers are made 
of iron, brick, glass, or wood, and a plant frequently in- 
cludes two or more kinds of chambers. Beyond the cham- 
bers proper, wooden channels often extend for hundreds of 
feet, the gases finally making their exit through a long 
flue. 

Purification of Mercury. Mercury may be purified from 
common metals by distillation. It may also be purified by 
treating it with dilute nitric acid. From mechanical im- 
purities it may be freed by forcing it through chamois 
leather; this also removes some of the metallic impurities. 
The same result is effected somewhat less perfectly by 
filtering through a cone of paper with pinhole aperture. 
Mercury in this country is put up in iron flasks at the 
mines, the flasks weighing 76.5 pounds when filled. 

Properties of Mercury. With the exception of the rare 
metal gallium, mercury is the only metal liquid at the 
ordinary temperature. As a liquid it is remarkable in that 
it neither wets nor adheres to most solids, except those 
metals with which it forms alloys. Its specific gravity at 
0° C. is 13.59. It solidifies at - 38.8° C., and boils at 357.2° 
C. It is a good conductor of heat and electricity. 

It is unaltered in air or oxygen at ordinary tempei a tare, 
but oxidizes when heated to near its boiling-point, the 
oxide being again reduced when heated higher. In air con- 
taining hydrogen sulphide it tarnishes. When agitated 



326 INORGANIC CHEMISTRY. 

with turpentine or triturated with powdered chalk or other 
inert substances, it is converted into a gray powder, which 
is thought to be a mixture of mercury with some oxide. 
This powder is used in making ointments and pills. Mer- 
cury forms an amalgam with all common metals except 
iron and platinum. It adheres to platinum. 

Hydrochloric acid does not act upon mercury. Strong 
sulphuric acid has no action in the cold, but hot it attacks 
it, forming mercurous and mercuric sulphates. Mtric acid 
acts upon it, forming mercurous and mercuric nitrates. 

Uses of Mercury. Mercury is used in the construction of 
thermometers, barometers, and other physical apparatus. 
It forms an amalgam with gold and silver, and is largely 
used for the extraction of these metals from their ores. Its 
use for this purpose is improved by adding to it a little 
sodium or potassium. Many of the amalgams are used in 
the arts, the most important being the amalgam with tin, 
used in the manufacture of mirror-glasses; this amalgam 
consists of about one fifth mercury. The mercury is placed 
on a level surface of tin-foil and the glass carefully slid 
on to remove the excess of mercury. The plate is then sub- 
jected for several days to considerable x^ressure by which 
the amalgam is made to adhere to the glass. 

The mixed amalgam of cadmium and copper or gold, and of gold, 
silver, and tin are used in dentistry. 

Mercury m the form of vapor, or finely attenuated, will 
produce mercurial poisoning, but when swallowed in sen- 
sible masses its injurious effects are believed to be mechan- 
ical rather than chemical. 

Compounds of Mercury. Mercury forms two classes of 
compounds, mercurous and mercuric. In the first it acts as 
a univalent, and in the second as a bivalent element, towards 
other elements. Only the most important of these com- 
pounds will be mentioned. 



METALLIC ELEMENTS. 327 

Cinnabar ; Vermilion ; HgS. It has already been stated 
that the native sulphide is the source of all the mercury ; 
the artificial sulphide is largely prepared and used as a 
pigment. The native sulphide does not yield the pigment. 
The artificial sulphide is prepared in two ways, the dry and 
the wet. By the first, the proper proportions of the mer- 
cury and sulphur are agitated together, and the black sul- 
phide of mercury thus obtained is sublimed. In the wet 
process the black sulphide of mercury is produced by pre- 
cipitation, and this is converted into the red sulphide by 
sublimation, or by the long- continued action of alkaline 
sulphides upon it. The red and black sulphides have the 
same composition and the change from one to the other is 
not chemical. 

Mercuric sulphide is not soluble in either of the three 
great mineral acids at ordinary temperature. It resists the 
combined action of the air, carbon dioxide, aqueous vapor, 
and light. These facts explain the permanence of vermil- 
ion colors. 

Chlorides of Mercury. There are two chlorides of mercury, 
each of which is of considerable importance. 

Mercuric Chloride ; Corrosive Sublimate ; HgCl 2 . This 
chloride is produced when the vapor of mercury is burned 
in chlorine gas. On a large scale it is prepared by distilling 
mercuric sulphate with common salt ; the chloride sub- 
limes, sodium sulphate being left behind, 

2NaCl + HgS0 4 (heated) = JSTa 2 S0 4 + HgCL. 

Corrosive sublimate is quite soluble in hot water, but much 
less so in cold. Its solution is extremely £>oisonous. It 
coagulates albumen, forming with it an insoluble compound 
which strongly resists putrefaction. For this reason it is 
largely used by naturalists in the preparation and preserva- 
tion of specimens. Its action on albumen makes this sub- 
stance an antidote, if properly administered, in case of 



328 INORGANIC CHEMISTRY. 

accidental poisoning from corrosive sublimate. Wood 
impregnated with a solution of corrosive sublimate is pro- 
tected from decay and the attack of parasites. Its use in 
the preservation of wood is now largely superseded by 
creasote. 

Mercurous Chloride; Calomel ; HgCl. This substance 
is insoluble, and is therefore produced whenever a soluble 
mercurous salt meets a soluble chloride in solution. This 
salt can be manufactured by adding mercury, in the proper 
proportion, to the reagents used in the manufacture of cor- 
rosive sublimate, when the calomel is produced instead of 
the sublimate. This is the principal salt of mercury used 
in medicine. 

Mercury Oxides. Mercury forms two oxides, Hg 2 and 
HgO ; the latter, commonly known as the red oxide, is the 
more important. This oxide is formed when the mercury 
is highly heated in air. When thoroughly incorporated 
with a fatty substance, like lard, it constitutes a poisonous 
ointment. The ointment is sometimes used to destroy 
parasites which affect animals. It is known as red mer- 
curial ointment. It is prepared for this purpose by decom- 
posing the nitrate of mercury by a gentle heat, or, better, by 
adding a little mercury and deoxidizing the nitrate : 

Hg (N0 3 ) 3 + Hg 2 = 3HgO + N 2 3 . 

The oxide parts readily with its oxygen, and is therefore 
sometimes used as an oxidizing agent in the laboratory. 

PLATINUM. 

Occurrence. No compound of platinum with a non- 
metallic element has been found in nature. It is always 
found alloyed with the other metals. The metals usually 
present belong to the platinum group, and are rhodium, 
iridium, osmium, ruthenium, and palladium; these metals 



METALLIC ELEMENTS. 329 

generally occur alloyed with each other and with the plati- 
num. The platinum metals are found in alluvial deposits 
similar to the deposits containing gold, indeed, gold is fre- 
quently present. 

Most of the platinum is obtained from the Russian de- 
posits in the Ural Mountains, near Goroblagodat ; some 
comes from Brazil, Peru, Colombia, Borneo, and it has 
been found in the United States, Canada, and Australia. 
The platinum alloys generally occur in small grains dis- 
tributed through the sands, from which it is separated by 
washing. The process of separating the platinum from the 
associated metals is largely a chemical one; it was formerly 
entirely so. The separation in this process was brought 
about by the action of aqua regia upon the native alloy, 
and depends partly upon the relative action of the strong 
and weak acids upon the different metals, and partly upon 
the different properties of the chlorides produced. The 
platinum has also been separated by smelting the ore with 
galena. The lead forms an alloy containing nearly all the 
platinum, from which it is separated by cupellation. 

Properties of Platinum. With the exception of osmium 
and indium, platinum is the heaviest of the elements, its 
specific gravity referred to water being 21.5. It is 234,000 
times as heavy as hydrogen. It is the most infusible of the 
metals. It can be melted by the oxyhydrogen flame, and 
by this means made into vessels. It is not affected by the 
air at any temperature, nor do any of the acids singly at 
tack it at common temperature. Concentrated sulphuric 
acid at high temperature acts slightly upon it. It is very 
malleable and ductile, and at white heat is weldable. It 
possesses the power of causing the combination of oxygen 
with other gases or vapors. 

It is dissolved by aqua regia, and the fused caustic alka- 
lies attack it, as do phosphorus, sulphur, arsenic, and car- 
bon at high temperature. It readily alloys with lead and 



330 INORGANIC CHEMISTRY. 

other easily fusible metals. Care should be taken that 
these substances be not heated highly in platinum vessels. 

The action of platinum upon gases may be shown by 
holding a piece of thin platinum foil in the flame of a 
Bunsen burner until it is red hot, then if the gas be turned 
off and on quickly, the escaping gas will keep the metal at 
a red heat, and may even relight it. This result is brought 
about by the influence of the metal in causing combination 
between the gas and the oxygen of the air. The tempera- 
ture of the foil may be too low to emit any light when the 
gas is turned on, but the oxidation occurring at its surface 
soon brings it to redness. Spongy platinum, obtained by 
decomposing the ammonium chloride of platinum, pos- 
sesses this actuating power to a higher degree than does 
the foil. 

Dobreiner's automatic lamp is lighted by means of 
spongy platinum. This apparatus consists of an alcohol 
lamp in connection with a little automatic hydrogen gener- 
ator. By pressing a lever a jet of hydrogen flows out and 
falls uj)on some spongy platinum. The oxidation that 
ensues rapidly raises the temperature until the vapor of 
alcohol from the lami>wick near the metal inflames. 

The oxidizing power of the metal was for a time made 
use of in the manufacture of acetic acid. The spongy metal 
caused the rapid transformation of the alcohol into acetic 
acid by inducing the oxidation of the alcohol. 

The precipitated form of platinum commonly called 
platinum Mack possesses this j)ower to a still higher 
degree ; hydrogen is instantly ignited by falling upon it. 
This form of platinum is capable of absorbing 800 times its 
volume of oxygen, and it absorbs and condenses consider- 
able quantities of other gases. The oxidation caused by it 
is probably in some cases due to the greater physical con- 
tiguity of the gases produced by the condensation. 

Platinum is employed in the form of wire, foil, dishes, 



METALLIC ELEMENTS. 331 

crucibles, forceps, tongs, retorts, and other laboratory appa- 
ratus. Its small coefficient of expansion jDerraits it to be 
fused into glass without subsequent cracking. Platinum is 
used in large vessels for retorts and coolers in the purifica- 
tion of sulphuric acid. 

Compounds of Platinum. Platinum forms two classes of compounds, 
the platinous and the platinic; in the first it plays the part of a dyad and 
in the second of a tetrad. The most important of the platinic compounds 
is the platinic chloride, perchloride, PtCl 4 . It may be prepared by dis- 
solving platinum in aqua regia. This salt is of value in the laboratory be- 
cause it forms slightly soluble double chlorides with the chlorides of the 
alkali metals and with certain organic hydrochlorides, and thus aids in 
detecting and separating these bodies. 

Other Metals of the Platinum Group. As already stated, the other 
metals included under this head are palladium, iridium, osmium, rhodium, 
and ruthenium, and they are generally found in association with platinum, 
alloyed with each other and with it. These metals resemble platinum in 
their unchangeable nature in air. Iridium is the most useful of this 
group. It is a hard steel-like metal, and is used for knife edges in deli- 
cate balances and for similar resisting surfaces. It generally increases the 
hardness of its alloys. Its alloys with platinum are important. The most 
refractory platinum vessels contain some iridium. These alloys were 
adopted by the Committee on International Standards for making standard 
weights and rules. 

Palladium is the most fusible of the group, its fusing-point being be- 
tween 1500° and 1700° C. Osmium is the heaviest of the elements yet 
discovered, its specific gravity being 22.39 to 22.42. 

Osmium forms a volatile tetroxide which is very poisonous. The native 
alloy of osmium and iridium is used to a limited extent for hard-wearing 
surfaces; this alloy is found most abundantly in Russia, California coming 
next in order of production. 

Palladium possesses the power of absorbing and condensing gases to a 
remarkable degree, and the metal has been used to a limited extent for 
wearing-surfaces in philosophical apparatus. 

The salts of this group have found no useful application. 

GOLD; Au. 

Occurrence. Gold occurs widely distributed in nature 
though in small quantities. It is nearly always found pure 



332 INORGANIC CHEMISTRY. 



or alloyed with other metals, but occasionally it is found 
combined with tellurium. The natural gold is most usually 
alloyed with silver, but sometimes with copper and other 
metals. 

METALLURGY OF GOLD. 

The sources from which gold is obtained in commercial 
condition come under three heads : 1st. From the auriferous 
ores of the metals ; 2d. From auriferous quartz veins ; 
3d. From sedimentary deposits, alluvial or marine.* The 
processes by which the gold is obtained from these sources 
may be limited to four, as follows : 1st. Smelting ; 2d. 
Amalgamation ; 3d. Leaching ; 4th. Simple washing by 
water. It is thus seen that the processes employed, except 
the last, bear the same names as those employed in the 
metallurgy of silver. The general method of treatment and 
the principles involved are very similar. 

Smelting. This process is applied only to the gold from 
the first source, and includes all that gold obtained in the 
smelting of argentiferous copper and lead containing gold. 
These processes have been described, and it is only neces- 
sary to state here that the gold after the smelting remains 
with the silver and is separated therefrom by acids or by 
electrolysis. Gold is thus obtained in considerable quan- 
tity at many smelters in this country, notably those in 
Montana, Arizona, and Colorado. The gold is, however, 
hot the principal product of these smelters. 

Gold ore from quartz veins is sometimes crushed and 
smelted with lead or copper ores, for the purpose of remov- 
ing the gold, but no additional principle is involved to 

* Gold has been found in the sands of certain sea beaches of the present 
day, notably in California, Oregon, and Australia, and it is known to be present 
in minute quantity in sea- water. At one time attempts, which were partially 
successful, were made to obtain gold from the beach sands of our western 
coast. 



; 






METALLIC ELEMENTS. 333 

those already described under the smelting for these metals. 
The gold from the quartz veins is almost always separated 
in the manner now to be described. 

Gold from Quartz Veins. In obtaining the gold from quartz 
veins there are usually involved two distinct processes: 1st. 
Amalgamation; 2d. Leaching or lixiviation. To secure as 
much gold as possible from the ore, it is generally sub- 
jected in succession to treatment by both processes. Occa- 
sionally only the first is employed, but the leaching pro- 
cess is less often employed alone. These processes are 
very similar to the corresponding processes for obtaining 
silver ; they will be briefly outlined. There are several 
distinct steps in each of the above processes, but the chemi- 
cal principles involved are simple. The gold-bearing rock 
is first broken and then stamped to a fine state of division 
in stamp batteries. These batteries are essentially similar 
to those described for the stamping of silver ores, and con- 
sist of an iron mortar and a stamp ; the latter are iron 
rods shod with steel which are lifted and dropped by ma- 
chinery. They weigh from 700 to 1000 pounds. By these 
stamps the ore is crushed until it is fine enough to pass 
through the perforated screens in the side of the mortar. 
The proper quantity of water is admitted to the mortar and 
carries the crushed ore through the screens. Gold mills 
are always wet-stamping. 

Amalgamation. The amalgamation may begin in the bat- 
teries or not until the pulp has passed through the screens. 
When amalgamation begins in the batteries the mortars 
are usually lined at the ends and on one or both sides 
with amalgamated copper plates. The mercury is charged 
into the battery. The mercury amalgamates the gold, and 
a large part of it is caught on the copper plates and 
inside the battery. Another portion of the gold is caught 
by appliances outside the battery. These appliances con- 
sist of inclined aprons or tables covered with amalgamated 



334 INORGANIC CHEMISTRY. 

copper plates, frequently arranged in descending steps, 
beginning just in front of the screens. The pulp, after 
passing through the screens, is carried by the water over 
the outside copper plates, which catch more of the free 
gold. The amalgamated copper plates are cleared off at 
intervals and the amalgam retorted to separate the gold; 
sometimes the amalgam is washed by grinding in a pan be- 
fore retorting. 

The pulp after leaving the copper aprons is made to flow 
over blanket-sluices. These sluices are covered with spe- 
cially prepared mill-blankets. The nap of these blankets 
arrests still another portion of the gold, while most of the 
sand and lighter minerals are carried over them. These 
blankets are removed at intervals and washed, and the 
washings are amalgamated in a special apparatus. This 
amalgam is retorted to separate the gold. When amalga- 
mation begins in the battery the blanket-sluices are less 
generally used. Whether the blanket-sluices are used or 
not, the sands or tailings carried away by the water are often 
subjected to further treatment. These tailings may be 
treated by amalgamation in grinding pans, but they are 
generally too impure to be treated in this manner, and are 
subjected to the next process to be described. 

Chlorine Leaching. Preliminaries. This process is 
seldom applied in this country directly to the ores from 
the mine, but is used to obtain the gold which is not caught 
in the amalgamation operations and which remains with 
the sands or tailings. As these sands contain only a small 
per cent of gold, the first step usually taken is to separate 
mechanically as far as practicable the gold-bearing material 
from that which carries no gold. This operation is termed 
concentration and is accomplished by the mechanical action 
of water upon the gold-bearing material. The object of 
concentration may be stated to be, to get out of compara- 
tively poor material a comparatively rich one. The process 



METALLIC ELEMENTS. 335 

of concentration is generally applied to the tailings, though 
it is sometimes used to convert a poor ore into a richer one 
before it is subjected to other treatment. 

The gold to which the leaching process is applied is in 
the metallic state, but so intimately associated with other 
minerals that the mercury has failed to reach it in the 
amalgamation. The minerals most commonly thus asso- 
ciated with gold in the concentrated tailings are sulphides 
of iron and other metals, the former usually constituting 
the larger portion. The next step after concentration is to 
roast the tailings to convert all the baser metallic com- 
pounds present into oxides, so that they will escape the 
action of the chlorine. 

CMorination. The roasted ore is subjected to the 
action of chlorine, by which gold chloride is formed. The 
chloride of gold is dissolved out of the chlorination-vat by 
lixiviation with water, and the solution received in a precip- 
itating-tank. The gold is precipitated from the solution 
in the metallic form by the addition of ferrous sulphate ; 
the precipitated gold needs only to be fused. The above 
method of chlorination is known as Platner' s process. 

Cyanide Leaching. The leaching of concentrated ores, as 
well as tailings which are comparatively free from sulphides, 
is now largely accomplished by treating with a weak solu- 
tion of potassium cyanide. This, in the presence of oxygen, 
forms a soluble compound with the gold, from which the 
metal may be recovered by precipitation by metallic zinc or 
by electro-deposition. 

The principles employed and the general methods pursued in the amal- 
gamation and leaching processes are outlined above, but the number of 
operations and the details of each vary with the kind and nature of ore. 
With some varieties of gold quartz so nearly all the gold is obtained by 
amalgamation that the tailings are not worth working. With some ores 
concentration may precede amalgamation instead of the reverse, as de- 
scribed above. Sometimes the amalgamation process is preceded by the 
roasting of the ores, and occasionally the ore is such that the leaching 



336 INORGANIC CHEMISTRY. 

process is not preceded by amalgamation. When the ores to be leached by 
chlorine are rich in silver there is usually added a little salt to the roasting 
charge and the silver is converted into the chloride. The silver chloride 
can be dissolved out before the ore is subjected to chlorination. Platner's 
chlorination process has been modified in this country by Mears', so that 
the chlorine is delivered under pressure into revolving amalgamating 
barrels. The gas acting under pressure and the agitation and friction of 
the ore give some marked advantages to this modification, but there are 
at the same time some disadvantages, one of the most marked being the 
escape of some of the compressed chlorine. Theiss improved on the Mears' 
method by generating the chlorine in the amalgamating barrel itself, 
though under less pressure the nascent chlorine was found to be very 
active, and the Theiss barrel method has found extensive application in our 
western country. 

Gold from Sedimentary Deposits. A large proportion of the 
world' s supply of gold has been obtained from sedimentary 
deposits. In this country the gold from this source is 
limited to alluvial deposits, but in the rich mines of South 
Africa which have recently come into such prominence the 
gold is found in the marginal sea deposits of previous ages 
which are now tilted and displaced and lie far inland. We 
shall first speak of the gold from the alluvial deposits of 
this country. 

Placer Mining. The gold from this source in this country 
is obtained by what is called placer mining. The placer 
deposits exist in the sands along the beds of the present 
streams or in the sands and gravels which now occupy the 
beds of channels and banks of extinct streams. The gold 
is separated from the sands mainly by the action of water. 

When gold was first discovered in California in 1848 a 
large amount of it was obtained by simple pan- washing. 
This process was followed by cradle- washing and then by 
sluice-working. As the shallow placers were exhausted 
and the working was extended to the deep placers of former 
river channels, hydraulic mining was developed. By this 
means it became possible to economically wash very large 



METALLIC ELEMENTS. 337 

masses of earth; in many instances several million parts of 
earth were worked to obtain one of gold. The large amounts 
of water and earth thus handled required very extensive 
appliances. The sluices were made from a few hundred 
feet to several thousand feet long. The great difference 
between the specific gravity of the gold and the sands (19.8 
and 2.6) rendered separation by washing possible, but amal- 
gamated copper plates, riffles, and mercury were used in the 
sluices to more perfectly catch the gold as the operations 
were extended. In these deep placers the richest sands 
were generally near the bed rock of the stream, and some- 
times were so consolidated that they had to be weathered 
or crushed before washing. 

In many places the deep placer deposits extended under 
rock formations that could not be removed. This led to 
drift mining. The auriferous sands from these mines were 
often found so consolidated that they had to be subjected 
to the milling and amalgamation process already described. 

Africa Gold Mines. The great mines of the Band in South Africa deal 
■with gold occurring in a hard conglomerate which was originally a margi- 
nal sea-deposit. These deposits were tilted and displaced and now form 
part of the interior highlands of the country. The sheets in which the 
gold occurs are called banket reefs. These reefs are mined exactly as are 
quartz veins. The ore is crushed in stamps and treated by the amalgama- 
tion process above described. The amalgamation is begun in the mortars. 
The tailings are concentrated and subjected to the chlorination or cyanide 
process of leaching as already described, the cyanide process being the 
more common.* 

Properties of Gold. Gold is a metal of great antiquity 
and has from the earliest times been esteemed a precious 
metal. In a pure state it is only about as hard as lead. It 
is the most malleable and ductile of metals. Its specific 
gravity is 19.3. For commercial purposes gold is always 
alloyed with some other metal to increase its hardness and 

* The action in the cyanide process is indicated by the equation, 4Au -f- 
SKCy + O a + 20H a = 4KAury a + 4K0H. 



338 INORGANIC CHEMISTRY. 

durability, silver and copper being the metals most gener- 
ally employed for this purpose. The gold coin of the United 
States is nine tenths gold, and one tenth copper alone, or an 
alloy of copper and silver. The purity of gold is generally 
indicated by carats; pure gold is 24 carats fine. Gold of 18 
carats is only three fourths fine. On account of its great 
malleability gold leaf can be made exceedingly thin. 

Gold is not affected by the atmosphere or moisture and 
does not tarnish. It is not acted upon by any of the ordi- 
nary acids, but is attacked by aqua regia or free chlorine. 
Common gold alloyed with copper may be made to present 
a pure gold surface by heating and oxidizing the copper 
and dissolving it out with sulphuric or nitric acid. The 
uses of gold are too well known to require mention. 

COMPOUNDS OF GOLD. 

Gold Chloride; AuCls. The most important of the inorganic salts of 
gold is the gold chloride, AuCl 3 . It can be prepared by acting upon gold 
with aqua regia. The chloride is very easily reduced to the metallic state. 
Organic matter generally, and nearly every substance capable of combin- 
ing with oxygen, will reduce it. The property of the salt together with the 
permanency of the deposited metal renders the chloride useful in photog- 
raphy. A protochloride is obtained by heating the trichloride. 

Oxides and Sulphides. Three oxides of gold have been obtained, but 
they are of no practical importance. Several combinations of gold with 
sulphur have been obtained, but their compositions are not well deter- 
mined and they are not of practical importance. The Purple of Cassius, 
produced when stannous and stannic chlorides are added to dilute solu- 
tions of gold, is used in enamel painting and in coloring glass. It gets its 
name from the discoverer, Andreas Cassius of Leyden. The exact com- 
position of this substance is not known, but it contains gold, tin, and 
oxygen. 



CHAPTER Y. 
ORGANIC CHEMISTRY. 

CHEMISTRY OF THE CARBON COMPOUNDS. 

The term organic chemistry was formerly used to de- 
note the chemistry of compounds found in the bodies of 
plants and animals. It was originally thought that these 
compounds could only be produced in living organisms, 
animal or vegetable, and that their production was due to 
the vital forces which were different from the chemical 
forces artificially brought into play in the laboratory. This 
view led to the separation of chemistry into two branches, 
organic and inorganic, the latter including the chemistry 
of those compounds whose existence in no way depended 
upon the vital forces. 

The assumption as to the action of the different forces 
in the organic and inorganic worlds was rendered untena- 
ble when it was shown that many organic compounds could 
be formed by the direct combination of elements, or by the 
transformation of inorganic compounds. The preparation 
of urea accomplished in 1828 by Wohler was the first step 
in the artificial formation of organic compounds from their 
inorganic constituents. Many organic compounds of great 
complexity have since that date been built up from the 
elements themselves, and it rs now universally recognized 
that the chemistry of the organic compounds is but a part 
of the general science of chemistry. 

339 



340 INTRODUCTORY OUTLINES. 

Organic compounds all contain carbon, and organic 
chemistry is really the chemistry of the carbon compounds, 
but on account of the large number of such compounds it 
is convenient to study them separately rather than in con- 
nection with the element carbon. For the sake of conven- 
ience the division of chemistry into two branches is still 
generally retained, though the original reasons for the 
separation have been shown to be erroneous. 

There is, however, a distinction between organic com- 
pounds and organized oodles. The former have a definite 
chemical composition ; many of them can be produced 
artifically and possess definite chemical and physical prop- 
erties ; organized bodies consist of mixtures of definite 
compounds and have only been produced under the influ- 
ence of vitality. The chemical relations of the organized 
bodies and the life processes which go on in them come 
under the head physiological chemistry. 

CLASSIFICATION OF CARBON COMPOUNDS. 

The compounds of carbon outnumber the compounds of 
all the other elements taken together. The elements most 
usually combined with the carbon in these compounds are 
hydrogen, oxygen, and nitrogen. A large number contain 
only carbon and hydrogen ; a still larger number consist of 
carbon, hydrogen, and oxygen ; many consist of carbon, 
hydrogen, and nitrogen ; and still others of carbon, hydro- 
gen, oxygen, and nitrogen. In addition to the four ele- 
ments named, sulphur and phosphorus frequently occur. 
In the carbon compounds from organic sources, the above 
named are the elements generally found, but almost all the 
elements, metals and metalloids, have been artificially in- 
troduced as constituents of these compounds, and some of 
the metals are found in the natural compounds. The classi- 
fication of carbon compounds, like all other classifications, 



ORGANIC CHEMISTRY. 341 

is based upon similarity of properties and characteristics 
of the bodies grouped together. 

The nature of the carbon compounds permits a much 
more perfect classification than is possible in inorganic 
chemistry. The members of the same class and the differ- 
ent classes are derivable from each other by comparatively 
simple reactions. 

The system of classification includes nearly all arti- 
ficially prepared carbon compounds and the greater pro- 
portion of those produced in living bodies, but there are 
many compounds formed in the vital processes of plants 
and animals whose chemical relations are not sufficiently 
known to permit their classification ; such are the alkaloids 
and the albuminoids yet to be mentioned. 

The compounds of carbon are usually grouped into thirteen classes 
based upon their rational or constitutional formulae, that is, the formulae 
which indicate the radicals that compose the compound. There are other 
classes whose rational formulae are not made out, based upon certain simi- 
lar characteristics. 

There are a great many carbon compounds which con- 
tain only carbon and hydrogen ; most of the other well- 
defined carbon compounds can with reason be considered 
as derived from these, so that the compounds of carbon 
included under the term organic are generally derivatives 
of those containing only carbon and hydrogen, known as 
hydrocarbons. It is not the purpose of this text to consider 
the varied relations between the different classes nor be- 
tween the members of the same class of the carbon com- 
pounds, and the classification of the compounds described 
will only be referred to when such reference helps to define 
and elucidate the characters which it is sought to set forth. 

The most general divisions of the carbon compounds, 
which include all those just referred to, are the fatty and 
aromatic groups. The bodies which make up the first 
group are derivatives of the hydrocarbons whose general 



342 INTRODUCTORY OUTLINES. 

formula is C n H 2n+2 (paraffin series) ; the second group is 
derived from the benzene series whose general formula is 
C n H 2n _ 6 . These two groups, fatty and aromatic, are very 
convenient for general reference. 

STRUCTURAL, OR CONSTITUTIONAL, AND RATIONAL FORMULA. 

The basis for the classification of organic compounds is 
usually partially indicated in their chemical formulae. 
Such formula? have already been referred to as structural 
formula?, but it will be of convenience hereafter to state 
somewhat more fully the significance of these formulae. 
By the careful consideration of the changes and the 
behavior of any chemical compound under a large variety 
of dissimilar circumstances it is believed that the order of 
combination of the atoms in the molecule in many such 
compounds has been determined. A formula which gives 
the fullest information as to the constitution of a compound 
is called its structural or constitutional formula. By such 
formula it is intended to indicate the connection between 
the atoms in a molecule. It should be kept in mind that 
the representation of the formula on paper is of no im- 
portance, as the formulae are intended to express the man- 
ner of combination and not the actual positions of the 
atoms themselves. Thus the constitutional formula of 
methyl-ether is determined to be 

H 

H— C— H H 

I I I 

O and of acetic acid is H— C— C—O— H. 

H— C— H H 



k 



A rational formula is one that, from the way in which 
it is written, indicates the manner in which a compound 






INTRODUCTORY OUTLINES. 343 

breaks up or is formed under certain conditions, or shows 
the relations of allied compounds to each other. It is an 
abridged constitutional formula, which indicates certain 
relations not shown in an empirical or molecular formula ; 
or it is a molecular formula so written as to indicate cer- 
tain chemical relations of the compound. Thus the formula 
for acetic acid may be written C 2 H 3 2 H to show that the 
acid is monobasic, or it may be written C 3 H 3 0,HO, which 
indicates the origin of the acid from certain salts. Since a 
compound may split up into different groups or radicals 
or may be formed in different ways, the same body may 
have a number of rational f ormulse, each of which indicates 
certain characters under certain conditions. This fact has 
already been illustrated in the supposed constitution of 
certain inorganic salts, but owing to the larger number of 
atoms in many organic compounds the principle of resolu- 
tion into rational formulae is much more frequently pos- 
sible. 

Isomerism and Polymerism. Isomerides or isomeric bodies 
are those bodies which have the same percentage composi- 
tion and molecular weight but show different properties. 
Those isomerides which differ in physical properties but 
whose transformation under the action of the same agents 
is similar are called isomers. Those isomerides which 
exhibit dissimilar transformation under similar circum- 
stances are called metamers. The phenomenon of isomer- 
ism is only explicable upon the supposition that the 
arrangements of the atoms in the molecules are different. 

Polymeric bodies or polymers are those which have 
the same percentage composition but different molecular 
weights and consequently different molecular formulae. 
The carbon compounds furnish many examples of isomers, 
metamers, and polymers. 



344 ORGANIC CHEMISTRY. 

HYDROCARBONS. 

Of the carbon compounds the simplest are those con- 
taining only hydrogen and carbon, and from these, as 
already stated, most of the others can be derived. The 
hydrocarbons furnish several series of compounds, and each 
series under the action of reagents yields derivatives, so 
that the possible number of carbon compounds is very 
great. These compounds frequently exhibit a characteristic 
not common among inorganic bodies, viz., their molecules 
contain a large number of atoms of the elements which enter 
them, thus rendering possible a great number of isomers. 

SATURATED HYDROCARBONS. 

Paraffin Series; Formula C n H 2n+2 . The only hydrocarbon 
containing only a single atom of carbon is methane or marsh- 
gas. Carbon being a tetrad and hydrogen a monad, it is 
evident that on the theory of valency the constitutional 
formula of marsh-gas must be represented thus : 

H 

I 
H— C— H, 

H 

indicating a saturated compound, or one in which there are 
no free units of valency. A consideration of the formula 
above given will show that the relation between the number 
of atoms of the two elements is such that there are no free 
affinities. The hydrocarbons of this series cannot form 
compounds with other bodies except by substitution; one 
or more of the atoms of the molecule must be removed to 
effect the introduction of others. Since hydrogen is a 
monad and cannot act as a connecting atom, it is evident 
that on the theory of valency the carbon atoms in hydro- 
carbons must be connected directly to each other. The 



PARAFFINS. 345 

different ways in which the connection may be made, and 
yet satisfy all the affinities of each element, is thought to 
explain the frequent occurrence of isomers. In the satu- 
rated hydrocarbons it is thought that no two carbon atoms 
are held together by more than one combining unit of each 
atom. 

Methane or marsh-gas is the lowest member of this series, 
the others containing more than one atom of carbon. The 
formulae of the consecutive members of the paraffin series 
differ from each other by CH 2 ; the first four are: methane, 
CH 4 ; ethane, C 2 H 6 ; propane, C 3 H 8 ; and butane, C 4 H 10 . Such 
a series is termed an homologous series. The highest 
known member of this series contains 35 atoms of carbon. 
The members of the series up to those containing four 
atoms of carbon are gases; from four to sixteen they are 
liquid at ordinary temperatures ; those containing a greater 
number than sixteen atoms of carbon are solid. 

Many of the hydrocarbons of the paraffin series occur 
abundantly in nature. The occurrence of methane as marsh- 
gas and fire-damp has already been referred to. 

Petroleum. The great natural source of this paraffin 
group is the petroleum oil, found most abundantly in this 
country and in Russia. It is also found in several other 
countries. 

American petroleum consists almost entirely of the 
paraffin hydrocarbons, though some of the benzene group 
are present in small quantities. The Russian petroleum 
contains a considerable per cent of the benzene hydrocar- 
bons and their derivatives. The petroleums are mixtures 
of the various members of these hydrocarbon series which 
can be separated from each other by fractional distillation. 
A large number of valuable products is derived from them. 

In this country the oil-wells are connected by pipe lines 
with the refineries at New York, Baltimore, Pittsburgh, 
Cleveland, and Buffalo. The lines in some cases are over 



346 ORGANIC CHEMISTRY. 

three hundred miles long and the oil is forced by pumps 
through the pipes from the wells to the refineries. 

At the refineries the oil is subjected to fractional distil- 
lation. The products which first come off as the tempera- 
ture rises are of course the gaseous products. The more 
easily condensible of these are collected, liquefied by pres- 
sure, and used to produce cold by evaporation, in the 
manufacture of ice, etc. This product is mainly composed 
of C 4 H 10 butane and is called cymogene. The names of the 
commercial products vary at different places ; some of the 
more important in the order of the boiling-points are rhigo- 
lene, used as an anaesthetic ; petroleum ether, used as a sol- 
vent for rubber ; gasolene, used for enriching coal-gas ; 
naphtha, used as the working substance in naphtha engines. 
Benzine, used as a solvent and largely substituted for turpen- 
tine, comes off between 120° and 150° F. ; it is entirely dif- 
ferent from benzene, the latter not belonging to the paraffin 
series. Kerosene is the product which distils over between 
150° and 300° F. and is the liquid so largely used as a burn- 
ing oil. It is jjurified by agitating with acid and in alka- 
line solution before it is put upon the market. There are 
many grades of this oil, depending upon the color and fire 
test to which the oil is subjected. The fire tests are in 
some cases fixed by law and differ in different places. An 
oil which when heated in an open vessel to 100° F. does not 
give off vapor enough to ignite when a flame is brought 
near its surface is safe under ordinary conditions of use. 

The residue of the crude oils after distilling off the 
kerosene is subjected to still higher temperature, and from 
it are obtained the lubricating oils and the solid paraffins. 
The lubricating oils are daily increasing in importance and 
are now used in immense quantities. The softer of the solid 
paraffins are called vaselines, of which there is a number 
of varieties. The more solid, wax-like paraffins are present 
only in small quantities in the American petroleum, less 



UNSATURATED HYDROCARBONS. 347 

than three per cent ; they reach ten per cent in the Burmah 
petroleums, and very much more in the petroleum from the 
shores of the Caspian. 

The greater proportion of the solid paraffin is prepared 
from the products obtained from the distillation of carbon- 
aceous shales. Scotland is the centre of the industry. In 
Germany and Austria large quantities of paraffin are ob- 
tained by the distillation of brown coal or lignite. These 
coals and shales also yield burning and lubricating oils 
similar to those from petroleum. 

Paraffin is tasteless and without odor, insoluble in water, 
but freely soluble in ether. It is largely used as a substi- 
tute for sulphur in dipping matches ; it is used in the 
manufacture of candles, in water-proofing and finishing 
cloths, and as an insulator in electrical apparatus. It has 
also been applied to preserve food from deterioration. 

Native solid hydrocarbons are found and known under 
the name of ozokerite. It is used in Europe in the manu- 
facture of candles. It closely resembles paraffin, but is 
thought to contain a smaller per cent of hydrogen. 

The petroleum industries of the United States are of im- 
mense extent and of vast importance. The burning and 
lubricating oils furnish one of our largest items of export. 
The refined oils are exported in tank steamers, and a num- 
ber of these steamers is engaged in such service, running 
between American and European ports. 

UNSATURATED HYDROCARBONS. 

All hydrocarbons which do not have the formula 
C n H 2ri+ 2 are found to be capable of uniting directly with 
certain other bodies without the removal of any of the 
constituent elements ; it is therefore assumed that in these 
hydrocarbons some of the carbon atoms are linked to- 
gether by more than one unit of valency of each. One of 
them, ethene, may be indicated thus : 



348 ORGANIC CHEMISTRY. 

H— C=C— H 

I I 
H H 

and acetylene thus : H — C=C — H. In the saturated com- 
pounds no atom is connected to any other by more than 
one unit of valency of each ; in the unsaturated two atoms 
may be connected by more than one unit of each. It is 
readily conceivable that in these compounds the atoms 
which are connected by more than one combining unit of 
each may extend this excess of affinity to other bodies, 
thus forming new compounds without removal of any 
atoms from the molecule. 

define Series. These are unsaturated hydrocarbons 
whose general formula is C n H 2n . The lowest member of 
the series is olefiant gas, ethene, or ethylene, C 2 H 4 , The 
series is an homologous one and results by the successive 
addition of CH 2 . 

The first three members of the series are gaseous, most 
of the remainder are liquid, but the four highest members 
are solid. The members of this series resemble in proper- 
ties the corresponding members of the paraffin series ; the 
boiling-points of the liquid members which have the same 
number of carbon atoms lie very close together. The series 
is obtained from petroleum oil and by the destructive dis- 
tillation of carbonaceous matter. Ethylene, the lowest 
term of the series, has already been mentioned in connec- 
tion with carbon ; the highest member contains thirty 
atoms of carbon. 

Acetylene Series. The general formula for the series is 
C n H 2n _ 2 . Acetylene is the lowest member of the series, and 
the homologues differ consecutively by CH 2 . This series, 
as the two preceding, consists of gases, liquids, and solids. 
Acetylene is the only hydrocarbon that can be produced 
artificially ; its production and uses were described under 
the element carbon. 



TERPENES. 349 

The terms of the olefine series differ from the corresponding terms of 
the paraffin series by two hydrogen atoms, and the acetylene series from 
the olefine series in the same manner ; the hydrogen, in proportion to the 
carbon, growing less in the series in the order named. The latter two 
series may therefore be considered as derivatives of the paraffin or methane 
series. 

Benzene Series; Aromatic Hydrocarbons. The general 
formula for the series is C n H 2n _ 6 , where n is a whole 
number not less than six. The homologues differ suc- 
cessively by CH 2 . On account of the fragrant odor of 
some of the benzene derivatives they were formerly termed 
aromatic hydrocarbons, but equally fragrant odors are 
found among the methane derivatives hence the term is 
no longer strictly applicable. 

Benzene. The lowest member of the series is benzene, 
C 6 H 6 . This body is the basis from which a large number 
of organic compounds may be derived. Benzene is pro- 
duced in the destructive distillation of many organic sub- 
stances ; it is also found in petroleum. It is present in con- 
siderable quantity in the more volatile portion of coal-tar 
oil, and this is the source from which it is principally ob- 
tained. The light oil from coal-tar is subjected to frac- 
tional distillation by which the benzene is separated and 
then purified. 

When pure it is a thin limpid liquid with an odor sug- 
gestive of coal-gas. It solidifies at 0° C. It is insoluble in 
water, but mixes with alcohol and ether. It dissolves sul- 
phur, phosphorus, iodine, and many fats and resins which 
are insoluble in water. It is manufactured in large quan- 
tity for conversion into aniline, from which are obtained 
many beautiful and useful dyes. Its vapor constitutes one 
of the illuminating constituents of coal-gas. 

Terpene Hydrocarbons. The empirical formula of this 
group is C 5 H 8 . They are volatile oils existing in certain 
plants ; they have not been formed by artificial processes, 



350 ORGANIC CHEMISTRY. 

Turpentine oil is the most important member of the ter- 
penes ; its formula is C 10 H 16 . It exists in the wood, bark, 
and leaves of many coniferous trees, and is generally pre- 
pared by distilling the thick juice which is obtained by tap- 
ping the trees, making incisions into the bark. This juice 
is a mixture of turpentine oil and resin. In this country 
turpentine is principally obtained from two varieties of the 
pine, the industry being most largely developed in North 
Carolina. 

Turpentine oil when pure is colorless and mobile ; it 
has a penetrating and disagreeable odor. Its boiling-point 
is 158-160° C. Its specific gravity is .86. It is but slightly 
soluble in water, but dissolves in strong alcohol, ether, and 
carbon disulphide. It burns with a smoky flame. It dis- 
solves iodine, sulphur, phosphorus, caoutchouc, resins, and 
many fixed oils. The consumption of turpentine oil or 
spirits in the preparation of paints and varnishes is very 
extensive. 

There is a large number of other essential oils belonging 
to this group which have the same empirical formula, and 
many of them the same molecular formula, as turpentine 
oil. Such bodies are the oils of lemon, juniper, orange, 
birch, etc. These oils are generally obtained by distilling 
the leaves, flowers, seeds, or other vegetable products with 
water, or by passing a current of steam through these 
products. The boiling-points of the oils are much higher 
than that of water, but they readily distil with aqueous 
vapor. When the vapors condense, the greater portion of 
the oil forms a layer on the surface of the water and may 
be entirely separated by shaking the water with ether or 
saturating it with salt. The ether dissolves the oil and can 
be separated by distillation. The salt causes the oil to 
separate from the water. In some of the more delicate per- 
fumes the distillation is accomplished in a vacuum or the 
oil extracted by pressure or dissolved out by carbon di- 



CAOUTCHOUC. 351 

sulphide. These oils, when not isomeric with turpentine 
oil, are mixtures of hydrocarbons, having the same per- 
centage composition as terpentine with compounds of car- 
bon, hydrogen, and oxygen. By exposure to the air they 
slowly absorb oxygen and lose their liquid state. They 
mix in all proportions with linseed, whale, and other fixed 
oils. The greasy stain communicated to paper by a volatile 
oil can be entirely removed by heating, which is not the 
case if it contains a fixed oil. 

Camphors. The camphors are crystalline bodies closely related to the 
terpenes, from which they appear to be formed by oxidation. Common 
camphor is obtained by distilling the chopped wood of the camphor laurel 
of China and Japan. It has been produced by the artificial oxidation of 
several terpenes. Camphor is very slightly soluble in water, but readily 
so in alcohol and ether. It burns with a smoky flame. Its formula is 

C J0 HiaO. 

Resins. The resins are closely related to the terpenes and appear to 
result from their oxidation. They are not definite compounds but mix- 
tures, the essential ingredients being certain resin acids which are rich in 
carbon and hydrogen and contain some oxygen. The resins are all, with 
unimportant exceptions, of vegetable origin. 

Common resin or colophony is the best example of the class. It is the 
substance remaining when crude turpentine is distilled and the oil of tur- 
pentine expelled. The resins are very widely distributed in the vegetable 
kingdom. They are insoluble in water, but dissolve in alcohol. 

There is a large number of resins used for industrial purposes. Shellac 
is employed in the manufacture of hats and is the chief constituent of 
sealing-wax. The many varieties of varnish are prepared by dissolving 
resins in alcohol. Mastic, dammar-resin, and sandarac are some of the 
common varnish-resins. Amber and copal are fossil resins, though the 
latter is also obtained direct from the trees. 

Balsams. These are natural mixtures of resins and essential oils, and 
sometimes acids. They are of different degrees of consistency, and by 
keeping the softer kinds become harder. 

Caoutchouc, India Rubber. Caoutchouc is closely allied 
to the terpenes. The substance of which it is mainly com- 
posed has a formula which is some multiple of C f) H 8 . The 
caoutchouc of commerce is obtained from some half dozen 



352 ORGANIC CHEMISTRY, 

different genera of tropical plants, including certain climb- 
ing plants as well as trees. If the source is a tree, an inci- 
sion is made in the bark and the exudation collected in 
earthen or tin cups. As these receptacles are filled they 
are emptied into larger vessels, all of which are brought 
together at some favorable location. The rubber juice is 
brought to a solid form by evaporating it from a sort of bat 
or shovel, which is dipped into the liquid juice and held 
over a fire until the moisture is driven off and a layer of 
caoutchouc left on the bat. The thickness of the layer is 
repeatedly increased by alternately dipping the bat into 
the juice and then drying it. When the layer has reached 
the desired thickness it is split up one side and removed 
from the form and hung up to be further dried. There are 
several other methods of preparing the caoutchouc from 
the milky juice, the object in each case being to get rid of 
the liquid in which the caoutchouc is suspended. The 
milky liquid is a solution of albumen holding about thirty 
per cent of caoutchouc in suspension. The manner in which 
the caoutchouc is dried and the source from which it is 
obtained account for the different forms that come into 
market. 

All raw caoutchouc contains albuminoid and resinous 
bodies and often mechanical impurities, as woody fibre, 
earthy matter, etc., from which it must be freed before it can 
be used for manufacturing purposes. The mechanical treat- 
ment of the caoutchouc is interesting and varies with the 
use to which it is to be put, but it cannot be described 
here. The best caoutchouc comes from the province of 
Para in Brazil and other provinces of that country. 
Caoutchouc also comes from Central America, Africa, 
Madagascar, Asia, and some of the East India Islands. 

Caoutchouc is almost equally valuable for its physical 
and chemical properties. Its lightness, elasticity, and 
impermeability to water are among its most valuable prop- 



CAOUTCHOUC. 353 

erties. Caoutchouc is insoluble in alcohol, but slowly dis- 
solves in carbon disulphide, naphtha, petroleum spirit, 
turpentine, and benzene, the last two being the best sol- 
Tents, but the petroleum solvents are as generally used 
because of cheapness. Caoutchouc is not acted upon by 
the alkalies or the dilute acids. It is slowly oxidized in 
moist air. It hardens and loses its elasticity by cold and 
softens and becomes sticky by heat. At about 120° C. it 
melts and decomposes into a black viscous mass which does 
not harden and is a valuable lubricant for air-tight stop- 
pers. 

Vulcanized Rubber. When caoutchouc is mixed with 
a small per cent of sulphur and the mixture heated to about 
150° C. it undergoes a most beneficial change and is said to 
be vulcanized. It is thought that some of the hydrogen of 
the caoutchouc is replaced by the sulphur and a sulpho- 
compound produced. The vulcanization of the rubber is 
accomplished after the rubber is mechanically purified. For 
this purpose about ten per cent by weight of sulphur is 
thoroughly incorporated with the rubber and the mixture 
subjected to the necessary temperature. Only a fraction of 
the entire sulphur seems to combine with the rubber, but 
the presence of the remainder is necessary to secure the 
effect. The vulcanization by heat is always accomplished 
after the rubber articles are made into required form. Such 
articles are moulded into shape, or the different parts cut 
out and joined together by rubber cement after the sulphur 
has been incorporated with the rubber. 

Certain other bodies besides sulphur are often added to 
the rubber. These are not known to act otherwise than 
mechanically, but seem to be beneficial; they are such as 
zinc, lead, and iron oxides, steatite, calcium, and lead car- 
bonates. 

Water-proof cloths are made by spreading the sul- 
phurred rubber in a plastic state by machinery upon the 



354 ORGANIC CHEMISTRY. 

surface of the fabric. Two pieces of cloth may be made to 
pass through rollers with their treated sides toward each 
other, thus forming water-proofing of double texture. The 
film of rubber spread upon the cloth may be made of any 
desired thickness. Water-proof cloths may be vulcanized 
by subjecting them to the required temperature or by what 
is known as the cold process. In this process the spread 
cloth is drawn slowly through a solution of sulphur chlo- 
ride in carbon disulphide, during which the thin rubber 
sheet takes up the required sulphur and need not be sub- 
sequently heated. The cold process is not as efficient as 
that first described. 

The effects of vulcanization are to greatly increase the 
elasticity of the rubber and to prevent its cohering under 
pressure and adhering to other bodies when warm. It is 
no longer affected by cold, its porosity is diminished, and 
it is not soluble in the solvents of common rubber. 

The water-proofing of fabrics by solution of rubber was 
patented by Mackintosh in 1824. Certain garments are 
still named from the inventor. The vulcanization of rub- 
ber was discovered by Groodyear in 1843. 

Vulcanite. With a greater proportion of sulphur 
(twenty to thirty-five per cent) and a still higher tempera- 
ture the rubber is converted into vulcanite or ebonite. It 
is much harder and more rigid than rubber, and is used in 
the manufacture of combs, rulers, discs, etc. 

Rubber Tubing and Threads. Rubber tubes are made 
in two ways. 1st. The rubber is brought to a semi-plastic 
condition and forced through an annular mould or die, con- 
sisting of two concentric cylinders with the necessary space 
between them. 2d. By cutting rubber bands of the proper 
width and joining their freshly cut edges by pressure, the 
bands being wrapped around a mandrel of the proper size. 

Rubber threads are either cut from the sheets or the 
semi-liquid rubber is pressed through sieve-like moulds. 



ALCOHOLS. 355 

The first method gives the rectangular threads, the latter 
the round. 

Gutta-percha. This substance has the same empirical 
formula as caoutchouc. It is, like that substance, obtained 
from exudation of certain trees. It comes mainly from the 
islands of the Indian Archipelago; its name signifies the 
gum of the perclia tree. The crude gum is procured in the 
same way as caoutchouc and is subjected to about the same 
mechanical process to free it from impurities. It is harder 
and less elastic than caoutchouc. It is not attacked by 
alkalies or dilute acids, but is acted upon by strong nitric 
or sulphuric acid. It is an excellent electric insulator, and 
is extensively used as a casing in submarine telegraphy, 
and for the covering of electric wires. It is largely used in 
the manufacture of medical instruments and for many 
cheap ornaments. 

Gutta-percha was for a long time obtained by felling the 
trees, the juice then exuding from incisions made at many 
places along the body and branches. This injudicious 
method was beginning to imperil the supply and has now 
been stopped. Because of the great demand for gutta- 
percha and caoutchouc, the English Government has at- 
tempted to cause the artificial production and spread of 
the parent trees. 

ALCOHOLS. 

This term is applied to a large number of bodies which in many respects 
differ widely from each other, but may all be considered as oxygen deriva- 
tives from the hydrocarbons. The relations of the alcohols indicate that 
they may be considered as derived from the corresponding hydrocarbons 
by the substitution of hydroxyl (OH) for an atom of hydrogen. Thus 
methyl-alcohol has the composition CH 3 , OH, which may be supposed to 
result by substituting (OH) for H in CH 4 ; propyl-alcohol has the composi- 
tion 3 Hb(OH)s , which results by substituting (OH) 3 for H 3 in propane, 
C 3 H 8 . It is evident, therefore, that they may be considered as compounds 
of hydroxyl and hydrocarbon radicals of different degrees of valency. 



356 - ORGANIC CHEMISTRY. 

Alcohols are said to be monatomic, diatomic, triatomic, etc., or mono- 
hydric, dihydric, trihydric, etc., according to the number of hydroxyl 
groups they contain. Each series of hydrocarbons has its derived alcohols. 
It will be necessary to refer to only a few of this large class of bodies. 

Alcohols of the Paraffin Series. The alcohols of this series are the most 
important of these bodies and embrace all of those that need to be referred 
to here. They may be considered as derived from the paraffin hydrocar- 
bons by the substitution of (OH) for H. 

Monohydric Alcohols. The lowest members of the series of alcohols are 
mobile liquids, the middle members are oily liquids, and those containing 
twelve or more carbon atoms are solids. 

There are two very important monohydric alcohols, the methyl-alcohol 
and the ethyl-alcohol, their formulae being CHsOH and C 2 H 6 OH; the cor- 
responding paraffins are methane (CBU) and ethane (C 2 H 6 ). 

Methyl- Alcohol ; CH 3 (OH). This body is popularly known 
as wood-spirit, and is found among the products which 
result from the destructive distillation of wood. The con- 
densed products from distilled wood separate into lighter 
*and heavier parts. The lighter part is the crude wood- 
vinegar and consists mainly of an aqueous solution of acetic 
or pyroligneous acid with a small proportion of methyl- 
alcohol. By fractional distillation the alcohol can be 
separated and purified. In the impure state, after one 
distillation, it is sold as wood-naphtha. Large quantities of 
methyl-alcohol are now made by distilling certain residues 
which result in the beet-root sugar factories, after the fer- 
mentation of the molasses for the production of common 
alcohol. 

Pure methyl-alcohol is very similar in smell, taste, and 
appearance to common alcohol. -It dissolves resins and 
volatile oils, can be burned in lamps, and for all these pur- 
poses can be used as a substitute for common alcohol. 
IVhen crude it has an offensive odor and a very disagree- 
able taste. 

Ethyl-Alcohol, Common Alcohol. This is the best and 
longest known of the alcohols and is generally designated 



alcohols. 357 

simply by the term alcohol. It is a monohydric alcohol 
derived from the second member of the paraffin series, 
ethane (C 2 H 6 ), by the hydroxyl substitution C 2 H 5 ,OH. 

Alcohol can be made artificially by the synthesis of its 
elements, C 2 H 2 being first produced, this converted into 
C 2 H 4 , and then into alcohol. 

Alcohol for commercial purposes is always obtained 
from the fermented products of certain kinds of sugar. 
Fermentation is a slow process of transformation which is 
brought about in certain organic bodies by means of sub- 
stances called ferments. All ferments are unstable nitro- 
genous bodies and may be divided into two classes : 1st. 
Those having an organized structure and capable of growth 
and multiplication ; 2d. Those without structure and in* 
capable of reproduction. 

The alcoholic or vinous fermentation, by which alcohol 
is produced from sugar, is brought about by a ferment of 
the first class called yeast, which is a vegetable micro- 
organism. 

If to a solution of grape or cane sugar (which contains 
in addition the necessary elements for the growth of the 
yeast) a little yeast be added, the process of fermentation 
will set up, during which the sugar will be converted into 
carbon dioxide and alcohol. The precise action of the yeast 
is not known, but it is during the growth of the yeast that 
the change is brought about. In the case of grape sugar 
or glucose (C 6 H 12 6 ) the molecule seems to split into carbon 
dioxide and alcohol, 

C 6 H 12 6 = 2C 2 H 6 + 2C0 2 . 

Cane sugar (C 12 H 22 O n ) is first converted by the yeast into 
glucose by the assumption of a molecule of water, 

C 12 H 32 O u + H 2 = 2C 6 H ia 6 ; 

the glucose is then resolved as before. 



358 ORGANIC CHEMISTRY. 

Note.' — During the fermentation other substances are produced, the 
most important of -which are glycerine, succinic acid, and fusel oil ; but 
about 95 per cent of the sugar may be converted into alcohol and carbon 
dioxide. 

Fermentation does not take place at a temperature below 
32° F. nor above 95° F. Many chemicals arrest and pre- 
vent fermentation, such as the strong acids and anti- 
septics. 

Pure yeast-spores will not ferment a pure solution of 
sugar, because the constituents for the growth of the yeast 
are absent. Water containing more than one half its 
weight of sugar in solution cannot be fermented by yeast, 
and the fermentation ceases when the alcohol produced 
constitutes one sixth the weight of the solution. The 
yeast increases greatly in weight when the necessary food 
constituents are present. 

The sugars most generally fermented for the production 
of alcohol are not those from the cane and grape, but those 
from the starch of grain and potatoes. The starch (C 6 H 10 O 5 ) 
is first converted into glucose (C 6 H 12 6 ) by the action of 
dilute acid, or into maltose (C 12 H 22 0ii + OH 2 ) by the process 
of malting yet to be described. 

The maltose undergoes the vinous fermentation under 
the action of yeast, just as do the other sugars mentioned.. 

By successive fractional distillations of the fermented 
solutions pure alcohol is obtained. 

Pure alcohol is a colorless mobile liquid, has a pungent 
odor, and a piercing, burning taste. Its boiling-point is 
below that of water (78° C), and it freezes at— 130° C. It 
burns with a pale blue flame free from smoke. It mixes 
with water in all proportions and has considerable affinity 
for it, absorbing its vapor from the air and abstracting it 
from animal and vegetable substances immersed in it. 
This fact partly explains its action in preserving bodies. 



ALCOHOLS. 359 

Its dilution with water results in contraction of volume 
and a considerable rise of temperature. 

Alcohol is very valuable in the laboratory as a solvent, 
standing next to water in this respect, It dissolves a large 
number of both organic and inorganic compounds and is 
especially useful in dissolving the resins, essential oils, 
etc. 

The strength of alcohol can be determined from its 
specific gravity, and tables are prepared for this purpose. 
Absolute alcohol has a specific gravity of .79 at 15° C. Its 
strength decreases as its specific gravity increases. So- 
called proof-spirit has a specific gravity of .92 and contains 
49 parts by weight of alcohol. If the alcoholic solution 
contains other bodies than water, the specific gravity, of 
course, does not indicate the strength. 

It may be observed that ethyl-alcohol is a homologue of 
methyl-alcohol, as appears from their formulae, CH 3 ,OH 
and C 2 H 5 ,OH, the two differing by CH 2 . 

The acetylene, olefine, and benzene series of hydrocarbons have their 
monohydric alcohols, which may be regarded as formed from these hydro- 
carbons in the same manner as the ordinary alcohols are formed from the 
paraffin series. 



These alcohols may be considered as derived from the 
paraffin hydrocarbons by the replacement of three hydro- 
gen atoms by three molecules of (OH). Only a few such 
are known. Only the most important one of these will be 
described. 

Glycerine ; Propenyl or Propyl-Alcohol. The basic member 
of the paraffin series for this alcohol is propane (C 3 IT S ) ; in 
this three atoms of hydrogen are replaced by three mole- 
cules of (OH), giving C 3 H 8 3 . 



360 ORGANIC CHEMISTRY. 

Preparation of Glycerine. It has already been stated that 
glycerine is produced during vinous fermentation, but it 
is always prepared by saponifying the natural fats. 

First Method. The natural fats are ethereal salts of 
the fatty acids, that is, salts of organic acids, in which 
the typical hydrogen of the acid is replaced by the alcohol 
radical. The more important of the animal and vegetable 
fats and oils are mainly composed of a fatty acid in 
which the hydrogen is replaced by the trivalent radical of 
propenyl-alcohol or glycerine (C 3 H 5 ). Such fats are there- 
fore termed glycerides ; and representing the fatty acid 
by HFt, the formula for the fat or ethereal salt will be 
C 3 H 5 Ft 3 . 

When these fats are boiled with a caustic alkali there 
is produced a soap and an alcohol, and the process is termed 
saponification. The reaction may be indicated thus : 

C 3 H 5 Ft 3 + 3KOH = C 3 H 5 (OH) 3 + 3KFt. 

The potassium salt of the organic acid is a common soap. 
The term saponification is not now limited to the actual 
production of a soap, but includes as well the processes by 
which ethereal compounds are resolved into an alcohol and 
a fatty acid. 

Second Method. Glycerine is now produced by the action 
of superheated steam upon fats, saponification by super- 
heated steam. The action of the steam is similar to that of 
the alkali and may be represented by the equation 

C 3 H 5 Ft 3 (fat) + 3H 2 = C 3 H 5 (OH) 3 + 3HFt. 

The chemical results of saponification are expressed in the 
above equations, and the subsequent preparation of glycer- 
ine is a question of purification. When pure fats or oils 
are saponified by steam, the glycerine and the fatty acid 
are both obtained pure. Crude glycerine is obtained in 






ALCOHOLS. 361 

large quantities in the preparation of soap and of the fatty 
acids. Glycerine has been prepared artificially. 

Properties of Glycerine. Pnre glycerine is a colorless 
viscid liquid without odor and with a very sweet taste. It 
readily absorbs moisture and mixes with water in all pro- 
portions. Its boiling-point is about 290° C, and it solidifies 
at about — 40° C. It burns with a bluish flame when heated 
to 150° C. At high temperature it volatilizes and partially 
decomposes, yielding acrolein (C 3 H 4 0), which gives the dis- 
agreeable odor often observed from a partially extinguished 
candle. 

Glycerine is a very powerful solvent, dissolving many 
substances more freely and some that water will not dis- 
solve. Glycerine is sometimes used in confectionery to 
sweeten, and by brewers to increase frothing in beer. 
Because of its attraction for water it is used to prevent 
certain bodies from becoming dry and hard, such bodies 
being moist with it, as sponges when used for cushions or 
mattresses. Its most important use is in the manufacture 
of nitro-glycerine and other high explosives yet to be 
described. 

By a comparison of the formulae of the three alcohols described it will 
be seen that they constitute an homologous series of which methyl-alcohol 
is the first term. These formulae will also show that ethyl- and propyl- 
alcohol may be considered as derived from the methyl-alcohol by the sub- 
stitution of a hydrocarbon radical for an atom of hydrogen: 



etc. 



f H 


rcH 3 

Ai 


fCH 5 


°i 


c ]i « 


(OH 


[OH 


[oh 


Methyl-alcohol. 


Ethyl-alcohol. 


Propyl-alcohol. 



The series might be continued to include other members of the monohydric 
alcohols. It will be seen by considering the formulae that the different 
alcohols appear to be derived from methyl-alcohol by the substitution of 
hydrocarbon groups for an atom of hydrogen. An alcohol from methyl by 
the replacement of only one atom of hydrogen by a hydrocarbon group is 
a primary alcohol; all of the above are primary alcohols. If two atoms of 



362 ORGANIC CHEMISTRY. 

hydrogen in methyl-alcohol are replaced by hydrogen radicals the result 
is a secondary alcohol, and if three be thus replaced it is a tertiary alcohol. 
The general formulae for primary, secondary, and tertiary alcohols would 
be represented as below, in which R stands for a hydrocarbon radical : 



R 
r H 
1 H 


R 
c R 


|E 


[oh 


[OH 


[OH 


Primary alcohol. 


Secondary alcohol. 


Tertiary alcohol. 



The formulas representing the constitution of the alcohols are the results 
of generalizing from many experimental facts, and they serve admirably to 
explain the facts. 

The oxidation of primary alcohols, by which hydrogen is removed and 
no other change in the atomic constitution produced, yields an aldehyde. 
The aldehydes from primary alcohols differ in constitution from the parent 
alcohol by two atoms of hydrogen; thus ethyl-alcohol by losing two atoms 
of hydrogen yields acetic aldehyde (C 2 H 4 0). The other primary alcohols 
yield corresponding aldehydes. The oxidation of the secondary alcohols 
with the elimination of hydrogen yields the ketones or acetones, which are 
the aldehydes of the secondary alcohols. 

ACETIC ACID. 

This acid is a member of a group of organic acids which may be 
considered as derived by oxidation of the primary alcohols or from the 
aldehydes of these alcohols. This group is generally called fatty acids, 
because many of them are contained in fats or derived from them. 

Preparation of Acetic Acid. Acetic acid occurs among the 
products of the destructive distillation of wood, and much 
acid is obtained from this source. The crude acid from 
wood is called pyroligneous acid and is found in the 
aqueous or lighter of the two layers into which the con- 
densable products of the wood separate. The acetic acid is 
generally obtained from the solution by first producing 
an acetate by the addition of a suitable base, then decom- 
posing the acetate by a less volatile acid. The acid liquor 
is generally neutralized by sodium carbonate and concen- 
trated to crystallization by evaporation. The sodium 



ACETIC ACID. 363 

acetate is carefully heated to expel tarry matter and 
distilled with sulphuric or hydrochloric acid : 

JS T aC 2 H 3 2 + H 2 S0 4 = C 2 H 4 2 + JNaHS0 4 . 

During this operation the acetic acid passes over and is 
collected. An impure acetic acid may be prepared by care- 
fully distilling the crude liquid without previous neutrali- 
zation. 

Alcohol may be oxidized to acetic acid by means of 
platinum black in a very short time. Some chemical 
works on the continent of Europe have employed this 
method. The power of the platinum to accomplish this 
oxidation is undoubtedly due to its power of condensing 
gases already referred to. The alcohol is placed in evap- 
orating dishes, in each of which stands a small tripod a 
couple of inches high. The tripod supports a smaller dish 
or watch-glass in which the platinum black is contained. 
By a suitable temperature the alcohol is volatilized and the 
vapor oxidized by the oxygen condensed on the platinum. 
The operation is accomplished in a suitable case or cham- 
ber to which the air has to be admitted at proper intervals. 
The pure acid is prepared by distilling the pure sodium 
acetate with pure sulphuric acid. 

The pure acid is a clear colorless liquid and has a 
pleasant but penetrating odor. It has a very sharp acid 
taste, and when pure blisters the skin. The boiling-point is 
118° C, and below 17° C. it is generally solid, constituting 
glacial acetic acid. Its vapor burns with a pale blue flame. 
Most of its salts are soluble, hence it cannot be readily 
precipitated. 

Acetic acid is largely used in the dilute form as vinegar 
and in the preparation of various acetates, many of which 
are used in the arts. The acid is an important solvent for 
many organic bodies and is accordingly valuable in the 
laboratory. 



364 ORGANIC CHEMISTRY. 

Preparation of Vinegar. Acetic acid is the acidifying 
principle of common vinegar. Yinegar is always made by 
the oxidation of alcohol, and the best vinegar is made by 
the spontaneous acidification of wine or cider. It is only 
necessary to expose the wine or cider to the action of the 
air at a suitable temperature. The alcohol present in the 
liquor is gradually converted into acetic acid by oxidation: 

C 2 H 6 + 2 =C 2 H 4 2 + H 2 0. 

The oxidation in this case is known to be brought about 
by a microscopic vegetable organism, mycoderma aceti, in 
the fermented liquor. The wine or cider contains the 
necessary ingredients for the growth of the organism, and 
the oxidation of the alcohol is in some way brought about 
by the plant. Fermented liquors are very liable to become 
sour owing to this action, but distilled liquors are not sub- 
ject to the change, since the food constituents for the 
organism do not exist in them. 

Yinegar is also made by mixing dilute alcohol or other 
distilled spirits with yeast or other nitrogenous organic 
matter and exposing it to the air. The added matter con- 
tains the constituents of growth necessary for the ferment, 
and the action is the same as for fermented liquors. The 
conversion of the alcohol into the acetic acid may be 
hastened by perfecting the exposure of the spirituous 
liquors to the air. The quick vinegar process consists in 
causing wine or other prepared alcoholic liquor to trickle 
through casks containing shavings, so as to expose a large 
surface to the air, the shavings having been steeped in 
vinegar to assure the presence of the ferment. 

Yinegar contains usually not over 5 per cent of acetic 
acid. In some countries it is permitted to add one tenth of 
one per cent of sulphuric acid to the vinegar to prevent 
further mothering. 



ACETIC ACID. 365 

In this country a large quantity of excellent vinegar is 
made by the farmers from cider. 

ACETATES. 

Acetic acid is a monobasic acid and forms a large num- 
ber of salts. Many of these acetates are employed in the 
arts, and some of the more important will be mentioned. 
All of the normal acetates are soluble. 

Aluminum Acetate. This salt is prepared by bringing 
together in solution common alum (double sulphate of alu- 
minum and potassium) and lead acetate. Lead sulphate is 
precipitated and separated by filtration. The solution of 
aluminum acetate is largely used in dyeing and calico- 
printing. The cloth is impregnated with a solution of the 
salt and subjected to a moderate heat or other process of 
fixing, by which it is converted into an insoluble basic ace- 
tate in the fibre of the cloth. The fibre is then capable of 
taking up and setting permanently the coloring matter. 
Such bodies are called mordants, and the acetates of the 
sesquioxides or weaker bases are the most useful, for they 
are most easily converted into insoluble basic salts. The 
sesquioxides of aluminum and chromium form very impor- 
tant acetates. The solution of aluminum acetate is gener- 
ally termed red liquor in the factories, owing to the fact 
that it is so often employed in fixing red colors. The red 
liquor may be prepared from aluminum sulphate instead 
of alum. 

Lead Acetate. This compound is prepared by dissolving 
litharge in acetic acid or by acting upon sheet lead with 
the vapor of acetic acid. It can be obtained in distinct 
crystals, but is usually indistinctly crystalline. It has a 
sweet taste and is frequently called sugar of lead. It is 
very extensively used in the preparation of alum mordants 
and in the manufacture of certain pigments. It is a valu- 
able article in the laboratory. 



366 ORGANIC CHEMISTRY. 

Copper Acetates. Verdigris is a mixture of several basic 
copper acetates, and results when copper is simultaneously 
exposed to the action of the air and the vapor of acetic 
ficid. It finds some use in oil and water colors, in calico- 
printing, and in the preparation of certain paints. 

Sodium Acetate is prepared by the action of acetic acid 
upon sodium carbonate. The solubility of the acetate in 
water increases very rapidly with the increase of tempera- 
ture, and the supersaturated solutions have been used in 
foot-warmers in certain European railways. The cooling of 
the heated solution is greatly retarded by the heat given 
out by the crystallization of the salt. 

Acetone; C 3 H 6 or CH 3 ,CO,CH 3 . Acetone is one of the 
products of the destructive distillation of acetates. It is 
usually prepared by the dry distillation of barium acetate. 

Acetone is a clear liquid, lighter than water, has an 
agreeable odor, and is important as a solvent. It is largely 
employed in dissolving nitro-cotton in the manufacture of 
smokeless powders. 

Acetic Ether; C 4 H 8 2 or CH 8 ,C0 2 ,C 2 H 5 . Acetic ether is pre- 
pared by distilling together alcohol, sulphuric acid, and 
sodium acetate. The ether is readily separated from the 
distillate. It is a fragrant liquid, with the odor often ob- 
served from cider. It is lighter than water, having the 
specific gravity of .91. It is a valuable reagent in the 
laboratory, and, like acetone, is used to dissolve nitro- 
cotton in the manufacture of smokeless powders. 

SOME IMPORTANT VEGETABLE ACIDS. 

Four of the more common vegetable acids are oxalic, tartaric, malic, 
and citric acid; they are all paraffin derivatives. 

Oxalic Acid. This acid occurs free in certain varieties of boletus 
(pink or touchwood mushroom), combined with potassium in sorrel and 
certain plants of the rumex (dock) species, in garden rhubarb, and as cal- 
cium salts in many plants. 

Oxalic acid is produced on the manufacturing scale by the oxidation of 



VEGETABLE ACIDS. 367 

highly carbonized organic bodies, such as starch, sugar, and cellulose. 
The principal commercial process now is by the oxidation of sawdust. 

The acid can be obtained in colorless transparent crystals which are 
soluble in less than their own weight of hot water and in about eight parts 
of water at 15.5° C. The solution has a very sour taste and is very poison- 
ous. Chalk or magnesia furnishes- the best antidote. 

This acid is largely used as a discharge in calico-printing and dyeing, 
for bleaching flax and straw, for removing ink and iron stains from linen, 
and for cleaning metals, marble, and wood. 

Oxalic acid is bibasic (C 2 H 2 4 ), and its metallic salts are in general 
soluble, that of calcium being least so. Calcium chloride may be used as 
test for a soluble oxalate. 

Tartaric Acid ; C^eOe. This term and formula include four isomeric 
bodies, but they differ in physical properties. The ordinary tartaric acid 
is the acid of tamarinds, mulberries, pineapples, grapes, and. several other 
fruits. It occurs in the pure state in small quantity, but is usually present 
in combination with potassium as an acid salt. The commercial supply of 
the acid is obtained from grape juice. 

During the fermentation of grape juice in the manufacture of wine an 
impure acid potassium tartrate is deposited, which is known as aryol or 
cream of tartar. This tartrate is dissolved and neutralized by the addition 
of powdered chalk or lime, by which calcium tartrate is precipitated. The 
calcium tartrate is heated with sulphuric acid, when calcium sulphate is 
formed and the tartaric acid left in solution, which can then be crystal- 
lized by evaporation. 

Tartaric acid is one of the most important vegetable acids. It is largely 
used in the cloth-printing industries both as a resist and as a discharge; 
also as a mordant in dyeing wool. It is remarkable as forming a very 
slightly soluble acid potassium tartrate when a potassium salt in solution 
is added to a solution of the acid, thus serving as a preliminary test for a 
potassium salt in solution. 

Tartaric acid forms a large number of single and double salts. Rochelle 
salt is a double tartrate of potassium and sodium. Tartar emetic is a 
double tartrate of potassium and antimony. Tartaric acid is bibasic. 

Malic Acid. This acid or its salts are widely distributed in the vege- 
table kingdom. The acid occurs in grapes, unripe apples, blackberries, 
and in considerable quantity in the garden rhubarb. It is generally pre- 
pared from the unripe berries of the mountain ash. 

Malic acid is bibasic and its formula is CjHoCh. 

Citric Acid. Citric acid occurs in large quantity in the juice of 
lemons, limes, bergamots, and is present in many other fruits and in the 



368 OBGANIC CHEMISTRY. 

sap of many plants. It is prepared in the largest quantity from lemon 
juice. This juice is neutralized by chalk, and the calcium citrate produced 
is decomposed by sulphuric acid. The uses of the acid are well known, 
Some of the citrates, as those of iron and magnesium, are used in medicine, 

The acid is tribasic, its formula being CeH 8 T . 

Tannic Acid, Tannin. This name has been given to a group of plant 
constituents which are capable of precipitating a solution of gelatine and 
of uniting with animal membrane, giving a more or less perfect leather. 

Gallotannic Acid. This is the best known and most important of this 
group and is generally called tannic acid. It is present in large quantity 
in gall-nuts, from which it may be obtained by digesting the powdered gall- 
nuts in an aqueous solution of ether. Upon filtering the solution and 
allowing it to stand, the ether separates from the water, carrying with it 
the coloring matter, the water containing the acid. By evaporation, the 
gallotannic acid is left as a yellowish, friable, amorphous mass showing no 
tendency to crystallize. A strong solution of gallotannic acid gives a pre- 
cipitate when mixed with sulphuric or hydrochloric acid. The acid 
precipitates albumin and gelatine. 

With ferric salts the acid gives a blue-black precipitate which is the 
basis of certain writing inks. A tincture of nut-galls is accordingly a 
delicate test for the presence of ferric salts. 

The tannins, extracted from the oak, hemlock, and similar species, and 
which are used for tanning leather, are closely related to the gallotannic 
acid, and are employed in tanning because of their similar action on 
gelatine. 

ALCOHOL ETHERS. 

This class of ethers may be considered as derived from 
the alcohols by replacing the hydrogen in the hydroxyl of 
the alcohol by an alcoholic radical. Thus in ethyl-alcohol, 
C 2 H 5 , OH, if the hydrogen of the hydroxyl be replaced by 
the ethyl-alcohol radical (C 2 H 5 ), we shall have C 2 H 5 OC 2 H5. 

We may also consider them as oxides of the alcohol 

p TT 

radicals p 2 -rr 5 0, or as anhydrides of the alcohols formed by 

the elimination of the water from two molecules of alcohol : 

2C 2 H 6 - H 2 = C 4 H 10 O. 

Ethylic-ether, Common Ether. This compound can be pro- 
duced by the action of several dehydrating agents upon 



ALCOHOL ETHERS. 369 

alcohol, but the process is not one of simple dehydration. 
Ether is made on a large scale by distilling a mixture of 
alcohol and sulphuric acid. The first action when the 
alcohol and acid are heated together results in the forma- 
tion of ethyl-sulphuric acid : 

H 2 S0 4 + C 2 H 5 OH - CjH 5 HS0 4 + H 2 0. 

When the ethyl-sulphuric acid is heated with more alcohol, 
ether results and the sulphuric acid is reproduced : 

C 2 H 5 HS0 4 + C 2 H 5 OH = C 4 H 10 O + H 2 S0 4 . 

This acid will act upon fresh alcohol, and if the supply 
of alcohol be properly regulated and the temperature kept 
within proper limits the etherification process can be made 
continuous. 

The continuous operation is effected by distilling the 
mixture of acid and alcohol in a retort arranged to admit 
fresh alcohol in regulated quantity, so that the temperature 
of the mixture is kept within the required limits, about 
140° C. 

The ether and water distil over and are condensed in a 
receiver together with some alcohol and a little sulphurous 
acid. The sulphuric acid is gradually used up, and the 
process cannot be continued indefinitely with the same 
supply of acid. 

To avoid the danger of contact of the alcohol vapor with 
flame, coils of tubing conveying superheated steam or the 
vapor of some liquid of high boiling-point are used as the 
source of heat. The distillate is shaken with water, which 
removes most of the alcohol, after which a base (lime, pot- 
ash, or soda) is added to fix the sulphurous acid. The re- 
maining water is removed by distilling over lime or calcium 
chloride. These operations may be partially repeated for 
greater purity. 

Properties of Ether. Ether when pure is a thin, mobile, 
transparent, and colorless liquid, with fragrant odor and 



370 ORGANIC CHEMISTRY. 

peculiar taste. Its. specific gravity at 15° C. is .70. Its 
boiling-point in the air is 34.9° C. Under atmospheric 
pressure it evaporates rapidly, producing great cold. It is 
very combustible and its vapor very dense, which proper- 
ties make careful handling necessary for safety. It mixes 
with alcohol in all proportions, but is only slightly soluble 
in water, one part in ten. This fact gives a means of sepa- 
rating it from alcohol when the latter is not present in too 
large a quantity. 

Ether is a solvent for resins, fats, alkaloids, and many 
other organic substances. It also dissolves phosphorus, 
iodine, and bromine. It is used to dissolve collodion cot- 
ton in photography and as an anaesthetic. 

CYANOGEN AND ITS COMPOUNDS. 

Cyanogen (C 2 N 2 ) is a colorless gas with the odor of bitter almonds. It 

is very poisonous. Cyanogen occurs in the gases of blast furnaces and can 

be prepared by heating silver cyanide strongly (AgCN). Silver cyanide is 

produced when potassium cyanide and silver nitrate are brought together 

in solution: 

KCN + AgN0 3 = KN0 3 + AgCK 

Potassium cyanide is always produced when nitrogen, charcoal, and potas- 
sium carbonate are highly heated together. Cyanogen is generally ob- 
tained by heating mercuric cyanide. In many compounds cyanogen acts 
like an element. It may be regarded as a monovalent group and is gen- 
erally represented by Cy. 

Hydrocyanic Acid; HCN. This acid, commonly known as prvssic 
acid, is found in the kernel of the peach and plum stones and in the leaves 
of the cherry and the laurel. It can be prepared by acting upon metallic 
cyanides with hydrochloric acid 

KCX + HC1 = KC1 + HCN. 

It is a colorless liquid and very volatile. The inhalation of the vapor is 
very dangerous, and the acid taken internally is one of the most fearful 
poisons known. 

Potassium Ferrocyanide. {ECX)^ Fe{CN)i,Aq. Yellow prussiate 
of potash, double cyanide of potassium and iron. This salt is the source 
of most of the cyanogen compounds, and is made on the large scale 






PHENOLS. 371 

by melting together potassium carbonate and iron filings or scraps, mixed 
with organic matter containing carbon and nitrogen. It crystallizes in 
large, lemon-colored crystals, readily soluble in water. This ferrocyanide 
is a chemical reagent of great importance and value ; with a large number 
of metallic salts it gives precipitates which are frequently very character- 
istic. It is largely employed in the manufacture of colors, in dyeing and 
calico-printing, and, as stated, is the source of many of the compounds of 
cyanogen. 

Potassium Cyanide ; KCN or KCy. This substance, as already stated, 
is produced when nitrogen is heated to a high temperature in contact with 
potassium carbonate and charcoal. It is also produced when potassium is 
heated in cyanogen gas or the vapor of hydrocyanic acid, but it is generally 
prepared by fusing the ferrocyanide of potassium with potassium carbo- 
nate. The cyanide then generally contains some cyanate and carbonate of 
potassium, but for most applications this impurity is not important. 

A solution of KCy dissolves the chloride and iodide of silver, in con- 
sequence of which fact it finds use in photography. It is used in the 
extraction of gold from its ores, and its double cyanide with gold and 
silver are used in electroplating and gilding. Its great solvent powers 
make it useful in cleaning gold and silver. 

Potassium Ferricyanide ; (KCN) 3 ,Fe(CN) 3 . This salt is often termed 
the red prussiate of potash. It is prepared by the oxidation of the yellow 
prussiate of potash. It is a powerful oxidizing agent in the presence of 
alkaline solutions ; such a preparation bleaches indigo. It is used in calico- 
printing. 

Mercuric Cyanide ; Hg(Cy) 2 . This cyanide is prepared by dissolving 
mercuric oxide in hydrocyanic acid. It is used to obtain cyanogen. 

There is a large number of other cyanides, the most important of 
which are certain complex cyanides used as colors. Such are Prussian blue, 
a complex cyanide of iron ; Hatchets' brown, a cyanide of iron and copper. 

PHENOLS. 

The phenols are benzene derivatives in which hydrogen 
of the benzene group is replaced by hydroxyl. They are 
derived from the benzene hydrocarbons in the same way 
that the alcohols of the fatty series are derived from the 
paraffins. 

Phenol, Carbolic acid, Plienic acid, Hydroxybenzene, 
C 6 H 5 OH. Phenol is found among the products resulting 



372 ORGANIC CHEMISTRY. 

from the destructive distillation of wood and coal. It is 
usually prepared from coal-tar, being the chief constituent 
of the acid portion of this tar. It is concentrated by col- 
lecting apart that portion of the heavy oil from coal-tar 
which distils over between 150° and 200° C. It is extracted 
from this distillate. 

Phenol crystallizes in colorless needles which have the 
odor of coal-tar. It liquefies at 42° C. and is then slightly 
heavier than water. It is soluble in Id parts of water at 
common temperature. It is poisonous, blisters the skin, 
and exerts an antiseptic action, arresting fermentation and 
putrefaction. There are several disinfecting powders which 
consist of carbolic acid mixed with mineral matter. 

CARBOHYDRATES. 

This term includes three groups of bodies each of which 
contains six atoms of carbon, or some multiple of six, and 
oxygen and hydrogen in the proportion to form water. 
These groups are nearly allied to each other and widely 
distributed in nature. 

The three groups are the glucoses, the sucroses or saccha- 
rides, and the amyloses. The first two groups constitute 
the sugars, the last includes the starches and the celluloses. 
The formula of the glucoses is C 6 H 12 6 ; of the sucroses, 
C^H^On ; and of the amyloses, (C^B. 10 O 5 )n. 

The first two groups are among the most important 
foods of the civilized nations, and the last supplies man 
with a large portion of both food and clothing. 

Some bodies are now classed among the carbohydrates which do not 
contains six atoms of carbon. The general formula of the glucoses is 
C n (H 2 0) n , but n is not always six ; of the sucroses, C n (H a O)n-i ; of the 
amyloses, (C 6 Hio0 6 )n. Several of the sugars have been shown to be 
aldehyde or ketone alcohols. 



GLUCOSES. 373 

GLUCOSES. 

Ordinary Glucose ; Dextrose ; C 6 H 12 6 . Ordinary glucose is the 
most important member of the glucoses. It exists in the 
juice of sweet grapes, in raisins, and in honey, of which it 
forms the crystalline portion. Its presence in urine is 
characteristic of the: disease called diabetes. 

Dextrose is made/on a commercial scale from starch by 
heating it with dd|Pte sulphuric acid. In this country it 
is made in enorj^pus quantities from corn-starch, hence is 
sometimes GBllec^om-sugar. The starch is obtained from 
maize or Indian corn and will be referred to under the 
subject of starch. In other countries starch from other 
sources is used. 

In this country the term glucose, among the manu- 
facturers, is limited to the liquid products, and such use of 
the term has become very general. The solid product is 
termed sugar. The manufacture of glucose in the United 
States is an immense industry, and the products in both the 
solid and liquid forms are very extensively used ; many 
kinds of syrup are composed of the liquid glucose, and the 
solid is largely" used in confectionery and as sugar. 

The conversion of the starch into sugar is accomplished 
by boiling it with water in large converters with from one 
to one and one-half per cent of sulphuric acid. The heat- 
ing is often done in closed converters and under consider- 
able pressure, steam being admitted for the purpose. The 
higher the pressure, the shorter the time required for the 
conversion. For the liquid glucose less acid and less heat- 
ing are required than for the sugars. During the heating 
the starch first passes into the isomeric dextrin, and this 
takes up the elements of water to form dextrose : 

(C (; H 10 O 5 ) w + (H 2 0)„ = (C 6 H 12 6 ) M . 
The acid is removed by the addition of powdered chalk, 
the liquid filtered through animal charcoal and evaporated 



374 ORGANIC CHEMISTRY. 

to the desired consistency. The evaporation is frequently 
done in vacuum pans. The glucose can be made perfectly 
colorless. A little cane syrup is often added to the glucose 
to give the desired color. Some glucose is employed in the 
preparation of artificial honey, the comb being made of 
paraffin. 

Liquid glucose obtained as above described contains 
considerable dextrin and maltose, with some organic salts 
of calcium. The first two substances are less abundant in 
the solid glucose. Chemically pure g^cose has to be 
obtained through further treatment. 

Dextrose is less sweet and the solid forms are less solu- 
ble than cane sugar. 

The cellulose of wood fibre can be converted into glucose, 
and some of the wood-paper manufacturers have attempted 
the commercial manufacture of glucose from this source. 

Fruit Sugar, Lcevulose ; CsHuOs. Fruit sugar nearly always ac- 
companies dextrose in the juice of sweet fruits. It is more difficult to 
crystallize than dextrose. It is sweeter than dextrose and less easy to fer- 
ment. A mixture of dextrose and lsevulose in equal proportions constitutes 
invert sugar. 

SUCEOSES. 

Common Sucrose, Cane Sugar ; C l2 H^O n . Cane sugar is 
the most important member of this group. It is very widely 
distributed in the vegetable kingdom, but is obtained on a 
commercial scale from only a few plants. The principal of 
these are the sugar-beet, sugar-cane, sorghum, sugar-maple, 
and a species of palm. A small amount is made in this 
country from the ash-leaved maple or box-elder and from 
melons. 

More sugar is now derived from beets than from any 
other single source. 

The manufacture of cane sugar is an important industry 
of many countries ; and only the general principles involved 
in the operations can be here mentioned. 



SUCR08ES. 375 

The juice is extracted from the cane by crushing between 
rollers. Lime is added to the juice to prevent the inversion 
of the sugar. It is also generally subjected to the action of 
sulphurous acid to prevent fermentation. The sulphurous 
acid may be introduced before the lime. The juice is then 
heated to coagulate albuminous matter, which rises to the 
surface as a scum. The liquid is separated from the scum 
and sediment, and evaporated to the crystallizing point. 
It is then allowed to cool and crystallize and the molasses 
drained off. This product is the raw sugar, and has to 
be still further treated to obtain refined sugar. . The refin- 
ing is accomplished by re-solution in hot water, filtration, 
and decolorization by passage through animal charcoal, 
and evaporation in vacuum pans. The steps in the prepara- 
tion of beet sugar are essentially the same as in cane sugar, 
but the juice of the beet is generally extracted by the diffu- 
sion process and not by macerating the beets and pressing 
the j)ulp. In this process the beets are cut into thin slices 
and subjected to the action of warm water, by which the 
juice is effectually extracted. The diffusion process has 
also been applied to the cane. 

Nearly all the beet sugar is made in Continental Europe. 
The cane sugar is derived from many localities, but mainly 
from Cuba, Java, Manila, Brazil, Mauritius, and Louisiana. 

Properties of Sugar. Many of the properties of sugar are 
too well known to mention. It melts at 160° C. and forms 
an amorphous mass upon cooling. If kept at that temper- 
ature for some time it is converted, without loss of weight, 
into dextrose and an uncrystallizable syrup, laevulosan 
(C 6 H 10 O 5 ). At a higher temperature it loses water and be- 
comes brown, yielding, according to Bloxam, caramelan 
(C 12 H 18 9 ). Caramel is composed of this body mixed with 
other substances and is the result of the action of heat 
upon sugar. Caramel is largely used to color alcoholic 
liquors and in confectionery. 



376 ORGANIC CHEMISTRY. 

Maltose ; CuH^On. This body results from the action of malt upon 
starch. The germinating grain (malt) contains a peculiar substance, dias- 
tase, which causes the starch to undergo hydrolysis, forming maltose and 
dextrose. Crystallized out of alcoholic solution, maltose has the same 
composition as cane sugar, but from aqueous solution its formula is 
C12H22O11 ,H 2 0. It becomes anhydrous at the boiling-point of water. 

AMYLOSES. 

Starch and Cellulose ; (C 6 H 10 O 5 )„. The best known and the 
most important members of the amylose group are starch 
and cellulose. 

Starch ; (C 6 H 10 O 5 ) w . This is one of the most widely dif- 
fused bodies of the organic kingdom. It occurs in all 
plants that have been examined, except certain fungi, and 
abundantly in the seeds of plants, especially of those 
cereals used for food. Rice, wheat, and Indian corn con- 
tain it in largest proportions. 

Fully two thirds or more of the food of mankind is de- 
rived from the carbohydrate group, starch furnishing much 
the largest proportion. 

Starch is necessary to the growth of plants, and its 
presence in the seeds fafifords nourishment to the young 
sprouts. 

Preparation of Starch. In the United States starch is 
generally prepared from maize (Indian corn); in England 
from rice and potatoes; on the continent of Europe from 
potatoes and wheat. The object in each case is of course 
to separate the starch from the other constituents. The 
outline of the method adopted in this country will give an 
idea of the principles involved in all cases. 

The cleaned grain (maize) is steeped in water for about 
thirty hours until soft enough to grind. It is then crushed 
by rollers or ground between millstones and washed upon 
sieves. The pulpy mass left upon the sieves may be re- 
ground and subjected to a second washing. The milky 
liquid carrying the starch flows into or over inclined boxes, 



AMYLOSES. 377 

known as starch-tables, during which time the starch 
grannies are deposited. The liquid passing on from the 
starch- tables flows into tanks in which are deposited cer- 
tain nitrogenous matters. This latter is mixed with the 
husks from the sieves and worked up for cow- and pig- 
feed, 

For further increasing the purity of the starch, by the 
removal of the nitrogenous matter, it is washed in a dilute 
solution of alkali (caustic soda) and again allowed to settle, 
the escaping liquid carrying off the nitrogenous matters, 
oils, etc. The starch is again thoroughly washed to remove 
alkali. The several subsequent operations are mechanical. 
The reports from some of the large American factories show 
a yield of starch equal to one half the weight of the maize 
employed. This indicates a heavy loss of the total starch 
contained. Single factories convert from five to twenty 
thousand bushels of corn daily. 

The starch from the potato may be obtained by steep- 
ing, crushing, and washing without the use of alkali. Rice 
contains the greatest percentage of starch, but the use of 
alkali is necessary to separate it from the other constitu- 
ents of the grain. In the manufacture of starch-sugar or 
dextrose, already referred to, the first step in the prepara- 
tion of starch is that above described. 

The finest qualities of starch are used for food, for mak- 
ing sugars and syrups, for sizing the finest papers, and for 
laundrying. The other varieties are largely used in the 
industrial arts, for weavers' dressing, for thickening mor- 
dants, etc. Besides the edible starches obtained from rice, 
potatoes, maize, and wheat, there are several other forms. 

Arrowroot The starch known under this name is ob- 
tained from the root of several kinds of plants widely dis- 
seminated in the tropics. The most important of these 
flourish in tropical America from Mexico to Brazil and in 
the West Indies. They belong to the genus Maranta. 



378 ORGANIC CHEMISTRY. 

The Brazilian arrowroot is frequently called cassava 
starch. 

Tapioca. This is a specially prepared form of the 
cassava starch ; other starches are obtained from the roots 
of various plants in widely separated places — Africa, 
Australia, East Indies, and China. 

Sago. This is starch obtained from the pith of certain 
varieties of the palm, indigenous to the East Indian 
Archipelago and the adjacent regions. These last named 
starches differ materially from the grain starches, in that 
they are more nearly pure starch, more readily gelatinize, 
and are thought to be more easily assimilated by the 
human system. 

Characteristics of Starch. To the naked eye starch appears 
as a white glistening powder, but under the microscope 
it is seen to have an organized structure, to consist of 
granules, generally ovoid, which are composed of concen- 
tric layers. The starch granules from different sources 
differ in appearance. The granules vary very much in 
size, those from the potato being -^ of an inch in the 
longest diameter, while those from certain plants, as 
cactus, are not over TTn j-(nr of an inch. Starch is without 
odor, is insoluble in cold water, and consequently without 
taste. The granules consist of starch-cellulose or farinose 
in the outer layers, the exterior layer being probably 
wholly composed of it. This cellulose is insoluble in cold 
water. The interior of the granules is partially soluble in 
cold water and is called granulose. The insolubility of the 
outer layer prevents the action of cold water upon starch. 
When a mixture of starch and water is heated to about 
70° C. the granules burst, the granulose is dissolved to a 
viscous liquid, slightly opalescent, due to the undissolved 
cellulose. The solution becomes gelatinous on cooling, 
and gum-like when dried. Iodine colors starch intensely 
blue, the action taking place upon the granules intact as 



AMYLOSES. 379 

well as upon the paste. Starch heated for some time 
to about 200° C. is partially converted into dextrin. The 
conversion into the soluble form is important in the prep- 
aration of foods. 

Dextrin; (C 6 i7io06)„. This body has the same formula as starch. It 
may be prepared by heating starch with dilute acids or by heating dried 
starch to a high temperature. Dextrin is soluble in water. There are 
several modifications of dextrin which are used as substitutes for gum. 

Gums. These are amorphous bodies occurring in many plants. They 
are insoluble in alcohol, but are soluble in water and form a viscous mass 
with it. Those which form a clear solution with water are real gums ; 
the others vegetable mucilages. 

Cellulose; (C 6 H 10 5 ) n . This substance is the principal 
ingredient in the framework of plants. It constitutes the 
walls of plant-cells and forms a large proportion of the 
solid parts of all vegetables. Woody tissue consists of the 
membranous cells together with encrusting material. 
When all encrusting material has been removed the 
cellulose is left. 

Fine linen and cotton are composed of nearly pure 
cellulose, the treatment to which the fibre is subjected 
having removed nearly all the other material. 

Pure cellulose is insoluble in nearly all ordinary 
solvents, is tasteless, and for a long time was thought to 
be absolutely innutritious, but this point is now thought 
to be doubtful. It is known to constitute a large part of 
the food of beavers. Cellulose is soluble in an ammoniacal 
solution of cupric hydroxide (Schweitzer's reagent). Cellu- 
lose is not colored by iodine. 

If unsized paper be steeped for a few seconds in a mix- 
ture of strong sulphuric acid and half its volume of water, 
and then washed with water and dilute ammonia, it is con- 
verted into a sort of parchment. It has the same composi- 
tion as cellulose and is called vegetable parchment. It is 
translucent, much stronger than paper, is very useful in 



380 ORGANIC CHEMISTRY. 

diffusion, and is largely used for baggage labels. It is not 
easily torn and withstands rain. 

Strong sulphuric acid converts dry cellulose into a gummy 
mass, which by the proper manipulation may be converted 
into dextrose and then into alcohol ; linen rags may thus 
be converted into alcohol. 

VEGETABLE COLORS. 

The vegetable kingdom exhibits great beauty and variety of color, but 
the compositions of the coloring principles have been determined in only a 
few cases, and only a few of the colors obtained directly from plants find 
application in the arts. 

The most universally distributed color in nature is green ; it is due 
to the presence of chlorophyl, which occurs in all the green parts of plants. 
Its composition is not known, though iron is supposed to be a constituent 
of it. Wax and other substances are associated with it, forming chlorophyl 
granules. 

The blue coloring matter present in certain flowers has been called 
cyanin. It is made red by acids ; consequently blue flowers cannot con- 
tain acid juices, while red flowers do. Bloxam attributes the color of cer- 
tain grapes and red wine to cyanin. 

Saffron, Turmeric, Madder, and Litmus are all vegetable colors. The 
litmus is obtained from certain varieties of lichens. It is made blue by 
alkalies and red by acids, the original color being a purplish red. 

Lac is a red coloring matter extracted from a resin of the same name 
obtained from a tropical plant. 

Carmine is a red dye obtained from the cochineal, the dried body of a 
species of insect which feeds upon a certain variety of cactus. 

Indigo. This is obtained from the indigo plant, growing chiefly in 
India, but also in China, Egypt, and South America. It has been known as 
a dye for many hundreds of years. It does not exist ready formed in the 
plant, but is the product of the alteration of the substance known as 
indican, which is nearly colorless. The indigo is obtained by macerating 
the plants in water and allowing them to ferment. The indican is con- 
verted first into white indigo and then by oxidation into the common or 
blue indigo. 

The above-named dyes are all composed of carbon, hydrogen, and 
oxygen, except indigo, which in addition contains nitrogen. Indigo is ex- 
tensively employed for dyeing woolen fabrics. 



ALBUMINOUS SUBSTANCES. 381 

ALBUMINOUS SUBSTANCES. 

This term includes a number of complex bodies found in vegetable and 
animal organisms all of which, in addition to carbon, hydrogen, and oxygen, 
contain nitrogen and most of them sulphur. Not much is known in regard 
to the constitution of these bodies, their molecular formulae not having 
been determined. The percentage numbers indicate great conformity in 
chemical composition, and the same conformity is shown in their general 
properties. The proportion of the nitrogen to the carbon, hydrogen, and 
oxygen is much higher than is usual in organic bodies. 

The albuminous substances are sometimes divided into two classes, 
albuminoids and proteids. The second more closely resemble common egg- 
albumin and are generally coagulated by heat ; the first, like bone-cartilage, 
yield gelatine with boiling water and are sometimes simply termed gelat- 
inous bodies. Again, both classes are sometimes included under the term 
proteids. 

Only a few of the most typical and common of the albuminous sub- 
stances will be mentioned here. 

Gelatine, Glutin. "When the skin, tendons, and organic matter of the 
bones of the animal body are subjected to the long continued action of 
boiling water, a solution is obtained, which, on cooling, solidifies to a trem- 
ulous transparent mass that becomes hard and brittle on drying. 

Cold water softens but does not dissolve gelatine. It is dissolved in hot 
water, and the solution gelatinizes on cooling. 

Tannin precipitates gelatine from its solution. The tissues which yield 
gelatim unite with tannic acid, forming an insoluble non-putrescible com- 
pound, or leather. 

Isinglass is a pure form of gelatine obtained from the bladder of the 
sturgeon and other fish. 

Glue and size are impure gelatines made usually from the parings of 
hides. 

Gelatine is largely used in food preparations, for clarifying wines, and 
in photography. Gelatine is sometimes called glutin. 

A gelatinous body closely resembling the animal gelatine is also obtained 
from silk. 

Albumins. There are several varieties of albumin differing but slightly 
from each other. These bodies are found in the blood, muscles, nerves, 
and other organs of animals and also in nearly all parts of plants, especially 
the seed. It is thought probable that these bodies are synthesized by the 
plant and then taken and appropriated by the animal with but slight 
change. 



382 ORGANIC CHEMISTRY. 

Egg-albumin. This exists in aqueous solution in the egg, and is one of 
the most common varieties of albumin. It is coagulated, and rendered in- 
soluble in water, by heat. Alcohol and ether also precipitate it from solu- 
tion. The raw albumin of the egg does not affect silver, but this metal is 
tarnished by cooked eggs, which also give a faint odor of sulphuretted 
hydrogen, indicating some decomposition in the cooking, by which H 2 S is 
liberated. 

Serum-albumin. This is abundantly present in the blood and other 
animal secretions. It closely resembles egg-albumin, but is not precipi- 
tated by ether. 

Plant-albumin. This occurs in nearly all vegetable juices. It is coag- 
ulated by heat and closely resembles the egg and serum albumins. 

Myosin. This is the albuminous substance present in solution in the 
sheaths of muscular fibres. Its spontaneous separation from the plasma 
after death produces the rigor mortis. 

Fibrin. Blood fibrin is the albuminous substance which separates 
from the blood during coagulation or clotting. It appears to be formed 
from soluble albumin in the blood by a change which is set up when the 
blood is removed from the vital influences. The clot is red, due to the en- 
tanglement of the red corpuscles in the fibrin. By washing, the fibrin may 
be separated into elastic filaments, which become hard and brittle upon 
drying. 

Vegetable Fibrin. This occurs in the undissolved state in plants, and 
especially in the cereal grains. When wheaten flour is kneaded upon a 
cloth with water, the soluble albumin and starch are separated and a tena- 
cious mass remains which is called gluten. When this gluten is boiled with 
dilute alcohol a portion is left undissolved and is called vegetable or plant 
fibrin. 

Milk Casein. Casein occurs in the milk of all mammalia, most plenti- 
fully in that of the carnivora. It is the chief constituent of the curd of 
milk. It exists in solution in the milk due to the presence of a little 
alkali. If the alkali be neutralized by the souring of the milk or the addi- 
tion of a little acid, the casein is separated. The most striking property of 
the casein is its coagulability by rennet, the mucous membrane of the calf s 
stomach. Casein does not coagulate spontaneously by heat. 

Vegetable Casein; Legumin. This substance is found most abun- 
dantly in the seeds of leguminous plants, as beans and peas. It closely 
resembles animal casein, and its solution is coagulated by rennet. 

Gluten. It is stated above that gluten is the name given to the tena- 
cious mass left when wheaten flour is kneaded upon a cloth with water. 



ALKALOIDS. 383 

When treated with ^boiling dilute alcohol, a portion of *the gluten is left 
undissolved and is called vegetable fibrin. As the alcoholic solution cools, a 
white floceulent precipitate is deposited which closely resembles the casein 
of milk; it is called mucedin. On adding water to the cooled solution a 
third substance is precipitated, which closely resembles serum-albumin, 
and is called glutin or gliadin. 

It is pertinent to recall here the fact that the albuminous substances of 
the animal organisms have their counterparts in the vegetable kingdom. 

ALKALOIDS. 

This name is given to a large class of nitrogenous vegetable compounds 
of a basic character. Many of them are of great medicinal importance 
because of the powerful action they exert on the animal system. They all 
contain carbon, hydrogen, and nitrogen, and nearly all contain oxygen in 
addition. They are soluble in alcohol and generally have a bitter taste. 

Caffeine ; Theine. This is the principal alkaloid of tea and coffee, in 
which it is thought to be present as a salt of some variety of tannic acid. 
Tea also contains a small quantity of some other alkaloids. Caffeine is 
composed of carbon, hydrogen, oxygen, and nitrogen. 

The fragrance which distinguishes prepared coffee does not belong to 
the raw berry, but is developed by the roasting. In the same way the 
aroma of the tea is developed by heat during the drying of the leaves. 
Each is due to a volatile aromatic oil produced by the heat. 

Nicotine. This is one of the alkaloids that does not contain oxygen. 
It exists as a salt of malic acid in the leaves and seed of tobacco. It is a 
volatile oily liquid. Nicotine and its salts are powerful poisons. Tobacco 
may contain from one to eight per cent of nicotine, but seldom over four. 
Tobacco contains an unusual percentage of mineral salts. This explains 
the large amount of ash it leaves upon burning. This ash may amount to 
one fifth the weight of the dried leaf. The salts are mainly the malate, 
citrate, and nitrate of potassium. The presence of these salts, especially 
the last, explains the smouldering combustion which these leaves undergo. 

Opium. This is the thick juice which is obtained from the capsules of 
the opium-poppy (popaver somniferum). It is a complex substance con- 
taining a large number of bases; one of the most abundant and best known 
of these is morphine. 

Morphine. This is obtained from opium, in which it is present often to 
the extent of ten per cent. It is a white powder, soluble in 500 parts of 
water, and has a bitter taste. Its formula (C17H19NO3) shows it to contain 
carbon, hydrogen, oxygen, and nitrogen ; and representing it by " M," the 



384 ORGANIC CREMISTRY. 

common medicinal form of morphine is MHC1, the hydrochloride of mor- 
phine or the muriate of morphia. 

The alkaloid present in opium in most abundance, next to morphine, is 
narcotine. 

Quinine. The bark of several species of the cinchona order contains a 
number of alkaloids usually associated with some vegetable acids. The 
best known of these is quinine, and this is the most important of the alka- 
loids. It is very largely used as a febrifuge. It is found most abundantly 
in the yellow cinchona or Peruvian bark. 

Quinine crystallizes in small crystals and to the naked eye appears as a 
white powder. It requires about 2000 parts of water to dissolve it, and its 
solution is alkaline and bitter. Its composition is indicated by the for- 
mula C20H24N2O2. The form of quinine generally used in medicine is the 
basic sulphate, which may be represented by Q 2 H 2 S0 4 ,Aq., in which Q 
stands for the formula above given. 

The cinchona barks were introduced into Europe from Peru in the first 
half of the seventeenth century by the wife of the viceroy of Peru, the 
Countess of Chincon, from whom they received their name. The cinchonas 
are indigenous to the slopes of the Andes between 7° N. and 20° S. The 
barks richest in alkaloids grow at an altitude between 6000 and 12,000 feet 
above the sea. The most highly prized cinchonas have been successfully 
cultivated in Java for nearly fifty years. 

Strychnine. This is obtained from the seeds and bark of the nux 
vomica, from St. Ignatius' bean, and from other tropical plants. It is 
slightly soluble in water, is bitter, and fearfully poisonous. It is said that 
it can be detected by its taste when dissolved in a million parts of water. 

Cocaine. This is obtained from the leaves of certain varieties of coca. 
Cocaine, in aqueous solution, is employed as a local anaesthetic, and finds 
extended use in minor surgical applications. In small doses it acts as a 
stimulant, and is one of the most insinuating of the poisonous drugs. Thp 
medicinal form most generally employed is the hydrochloride, BHC1. 



CHAPTER YI. 

IMPORTANT INDUSTRIAL APPLICATIONS 
OF CHEMISTRY. 

HEAT OF COMBUSTION. 

CALORIFIC VALUE OR POWER. 

The heat of combustion of a substance is the amount 
of heat expressed in thermal units that is evolved during 
its complete combustion. In the case of fuels this heat is 
frequently termed calorific value or power. 

The determination of the heat of combustion by ex- 
periment has proven itself a very difficult problem, but it 
has been accomplished in the case of a number of bodies. 
These determinations show that the methods of computing 
the heats of combustion which have long been followed 
and are still in general use are erroneous and unsatis- 
factory. 

This method of computation is based upon Welter's 
rule, which assumes that the heat developed by the per- 
fect combustion of an organic substance is equal to the 
sum of the heats due to the combustion of its elements 
when no oxygen is present : when oxygen is present, it is 
assumed that only so much of the hydrogen burns as is in 
excess of that necessary to form water with the oxygen 
present. In other words, 'it is assumed that the oxygen 
present is combined with the hydrogen in the propor- 
tion to form water, and that the oxidized hydrogen adds 
nothing to the heating power. This form of computation 
is illustrated by the following example : 

Example. — Required the calorific value of 75 pounds of wood. 
Molecular formula of wood is taken as C 6 H 9 04 = CeII(HaO)« , molecular 
weight = 145. 

385 



3S6 APPLICATIONS OF CHEMISTBT. 

In 1-45 pounds of wood there are 

72 pounds of C. 1 pound of C produces 8080 units of heafc. 

1 pound of H. 1 pound of H produces 34200 units of heat. 

72 pounds of H 2 0. 
Units of heat produced by the carbon in burning = 72 x 8080 = 581760 
Units of heat produced by the hydrogen in burning = lx 34200 = 34200 

Total heat produced by the 145 pounds of wood = 615960 

615960 
Hence the calorific value of 75 pounds of wood = — — — x 75 = 318600. 

14o 

To illustrate the inaccuracy of results from computa- 
tions based upon the above rule, the heats of combustion 
of a number of bodies as given by computation and from 
experimental determinations are here inserted. The first 
four hydrocarbons of the methane series give : 

Computed. Exper. a b 

Methane, CH 4 14610 13244 2119 iKQK 

lo8o 
Ethane, C 2 H 6 13304 12350 3705 

Propane. C s Hb 12830 12030 5293 

Butane, C 4 H 10 12584 11848 6871 

For the ethylene series we have : 

Computed. Exper. a b 

Ethylene, C 2 H\ 11811 11907 3334 15g3 

Propylene, C 3 H 6 11811 11731 4927 

Butylene, C*H 8 11811 11618 6506 

Pentylene, C 5 H 10 11811 11537 8076 

The four alcohols give : 

Computed. Exper. a b 

Methyl alcohol, CH 4 5167 5266 1685 1fJR1 

Ethyl alcohol, C 2 H 6 7190 7057 3246 

Propyl alcohol, C 3 H 8 8268 8018 4811 

Butyl alcohol, C 4 H,uO 8940 8616 6376 1565 

The four following carbohydrates give : 

Computed. Exper. 

Dextrose, C 6 Hi 2 6 3232 3692 

Cane-sugar, Ci 2 H 22 0ii 3400 3866 

Cellulose, C 6 Hi„0 5 3391 4146 

Starch, C 6 H 10 O 6 3591 4123 



CALOBIFIC INTENSITY. 387 

The first column of figures gives the heats of combus- 
tion by computation for one pound of each of the bodies, 
the second column gives the experimental determinations 
for the same weights. Column "a" gives the heats of 
combustion from experiment when a number of pounds 
equal to the molecular weight is employed ; column "b" 
shows the difference between the consecutive numbers in 
column "a". To avoid large numbers the units em- 
ployed in "a" and "&" are one hundred times as great 
as the ordinary unit — in other words, the numbers in these 
columns must be multiplied by 100 to express them in the 
same units as the first two columns. 

It is seen from column "5" that when molecular pro- 
portions are considered each addition of CH 2 increases the 
heat of combustion by nearly the same amount. The 
differences between the first and second columns show 
that the computed heats of combustion differ from the 
true by considerable amounts, According to the funda- 
mental principle of Thermochemistry (p. 73) these differ- 
ences in series one and two should give the heats of forma- 
tion of the compounds from their elements, if they could 
be so formed. 

CALOBIFIC INTENSITY. 

Calorific intensity may be defined as the temperature 
to which the heat generated by the burning fuel could 
raise the products of its own combustion. ISTo exact 
method has been devised for determining calorific inten- 
sity by experiment ; it is therefore computed from the 
calorific value. In the case of pure carbon, burning to 
carbon dioxide, the calorific intensity may be obtained 

C 
from the following formula : T = ^.t— , in which T is the 

calorific intensity, C the calorific value, W the weight of 
the carbon dioxide produced, and S the specific heat of 
the carbon dioxide. 



388 APPLICATIONS OF CHEMIBTRY. 

In determining the calorific x^ower of hydrogen, the 
vapor of water resulting from its combustion was con- 
densed in the calorimeter ; the heat which was latent in 
the vapor became sensible and was properly included in 
the calorific value, but when the vapor is no longer con- 
densed, this heat cannot be considered in the production 
of temperature, and must be deducted from the calorific 
value in computing calorific intensity. 

In fuels containing oxygen, the oxidized hydrogen ex- 
isting or supposed to exist as water is vaporized by part 
of the heat of combustion. This number of heat units 
must also be deducted from the calorific value of the fuel 
in calculating the intensity. 

The formula for the calorific intensity of fuel, like 
wood, containing hydrogen, carbon, and oxygen, is 

T= C_(B) 



WS + W^ + etc.' 

in which T is the calorific intensity ; C, the calorific value ; 
B, the latent heat of steam produced, which comes partly 
from the combustion of the free hydrogen in the fuel, and 
partly from the combined oxygen present as water in 
the fuel ; "W" and W y are the weights respectively of the 
carbon dioxide and the water vapor produced ; S and S, 
are the specific heats respectively of the carbon dioxide 
and the water vapor. 

The calorific intensity is independent of the weight of the body burned, 
but is dependent upon the time and atmosphere in which the combustion 
takes place. 

GLASS-MAKING. 

The manufacture of glass is a very ancient industry, the 
earliest examples being of Egyptian origin. A lion' s head 
of glass found at Thebes and now in the British Museum 
bears an inscription which places its date at 2400 B.C. In 



GLASS-MAKING. 389 

the tombs of Beni Hassan, dating at least 2000 B.C., the pro- 
cess of glass-blowing is represented. These two facts prove 
that glass was made more than four thousand years ago. 

Glass is a mixture of several insoluble silicates, and is 
destitute of crystalline structure when not too slowly 
cooled. One of the silicates present is always that of an 
alkali metal, potassium or sodium, and with these are asso- 
ciated one or more of the silicates of calcium, barium, lead, 
iron, or zinc. The mixtures of these silicates display prop- 
erties that are not possessed by the single silicates. The 
presence of alkaline silicates is necessary in the glass, for 
these silicates when fused dissolve silica readily, fuse more 
easily than any other class, and exhibit less tendency to 
crystallize on cooling. The silicates of the other metals 
named are more infusible and less readily acted upon. By 
mixing the silicates in the proper proportions the requisite 
properties are obtained in the glass. 

The most valuable and important projjerties of glass are 
its transparency, its plasticity before complete fusion, and 
its permanency. There are a great many kinds of glass, 
differing more or less distinctly from each other, depending 
upon the proportions of the constituents. The two most 
important divisions may be based upon the silicates pres- 
ent. First, the glass which contains alkaline and calcium 
silicates; and second, that which contains alkaline and lead 
silicates. To the first class belong the common window- 
glass, plate glass, and crown glass; to the second belong 
the flint or crystal glass and the material of artificial 
gems. 

Common window-glass is composed essentially of sodium 
and calcium silicates, and is made by fusing together the 
proper proportions of sand, calcium carbonate, and sodium 
carbonate. It usually contains a little aluminum silicate, 
owing to lack of purity in the materials employed. 

Plate glass has essentially the same composition as 



390 APPLICATIONS OF CHEMISTRY. 

window-glass, but is made from purer materials. Usually 
some potassium carbonate replaces some of the sodium as 
an ingredient. 

Crown glass is composed of the silicates of potassium 
and calcium, and is made by fusing together the proper 
proportions of sand, potassium carbonate, and calcium car- 
bonate. Potassium is less likely to impart color to the 
glass than sodium. This glass is generally employed for 
optical- purposes. 

Bohemian glass contains the same constituents as crown 
glass, but has a larger proportion of silica, to which is due 
its greater permanency and inf usibility. 

Lead or Flint Glass. This glass is made by fusing to- 
gether in proper proportions silica, lead oxide, and potas- 
sium carbonate. The oxide of lead generally used is the 
Pb 3 4 . The higher oxide is preferred because the excess 
of oxygen serves to oxidize any organic impurities that 
might accidentally be present, 

Other Glasses. Colored glass is made by fusing certain 
metallic oxides with the ingredients of any of the above- 
named glasses. 

The glass from which bottles are generally made has 
essentially the same composition as common window-glass, 
though containing less sodium, and in addition some iron 
silicate, to which its color is due. 

The red oxide of copper gives a red color to glass; cobalt 
oxide a blue color; oxide of manganese an amethyst color. 

Production of Glass. The principle of glass manufacture 
is simple. The materials of the glass are fused together 
and the silica combines with the metallic oxides, forming 
silicates. 

The fusing was formerly accomplished in large pots or 
crucibles of refractory fire-clay. The pots varied in size 
from three to five feet high and two to four feet in diame- 
ter. A number of these pots were accommodated in a single 



GLASS-MAKING. 391 

furnace and heated by gaseous fuel, which played around 
the pots. With lead-glass, covered pots were required to 
prevent the reduction of the lead to the metallic state by 
the gases of the fuel; in other cases the pots were open. 

In the past dozen years the pot furnaces have been 
largely replaced by the open-hearth or tank furnaces; this 
is especially so in the manufacture of bottles and of win- 
dow-glass. Some of these modern furnaces are of astound- 
ing dimensions, being from sixty to seventy-five long, from 
four to six feet deep, and from ten to twelve feet wide, and 
capable of containing over four hundred tons of melted 
glass. 

The fused constituents of the glass are converted into a 
great variety of finished products by processes which differ 
depending upon the kinds of products desired. In gen- 
eral, after the constituents are fused together the manu- 
facturing operations may be grouped into four. 

1st. Crown and Sheet Glass. A hollow glass sphere is 
obtained by blowing ; this for crown glass is converted 
into a flat disk by rapid rotation. For sheet glass, the 
globe is opened and extended into a cylinder, then split 
longitudinally, spread into a sheet, and flattened by 
suitable tools. Window-glass is generally made in this 
way. 

2d. Plate glass. This is made by pouring the fused 
glass upon a flat table and subsequently grinding and 
polishing it. 

3d. Hollow Ware. Under this head are classed all 
kinds of bottles, as well as the more delicate glasses, 
vases, etc. Bottles are always made by blowing the glass 
into moulds, both the external and internal r^ortions of 
the bottle assuming the shape of the mould. The process 
is a very rapid one ; a set of five men generally work 
together in moulding bottles. They usually average two 
or three finished bottles per minute. 



392 APPLICATIONS OF CHEMISTRY. 

Wine-glasses, vases, pitchers, etc., are made by blow- 
ing and hand manipulation, little use being made of 
patterns or moulds. Such ware requires the greatest 
manual skill and can only be fashioned by the most expert 
workmen. 

4th. Pressed Glass. Many kinds of glassware for 
domestic purposes are now made by moulding into shape 
by pressure. The external form is given by the mould, 
and the internal by the shape of the plunger. This 
process has brought into use a very cheap ware suitable 
for nearly all domestic purposes. The lead glass was. 
found most suitable for pressed ware, but to diminish cost 
the lead oxide has been replaced by barium carbonate, 
which gives a clear glass suitable for this manufacture. 

All finished glass products require to be annealed to 
avoid spontaneous fracture. 

By using a certain kind of glass called strass as a base 
all the precious stones except opal can be imitated. The 
production of artificial gems is an important feature of 
glass manufacture. 

Dexitrified Glass. Certain kinds of glass containing but little alka- 
line silicate may be made to partially crystallize by heating nearly to 
the fusing-point and then cooling slowly. It thus becomes opaque and 
is sometimes called Keamur's porcelain. It may be made transparent by 
refusion. 

Soluble Glass. If silica be fused with an excess of sodium or potas- 
sium carbonate it forms a glass which is soluble in water — a solution of 
which is sometimes used in making artificial stone. If sand be moistened 
with it and pressed into shape and heated highly, the glass fuses and 
binds the whole together. It is also used to preserve natural stone from 
decay, in mural painting, and in rendering wood non-inflammable. 

The glass industries of the United States are mainly 
centered in New York, New Jersey, and Pennsylvania. 
The abundance of suitable sand in this country affords 
marked advantages for this industry. Nearly all the sand 
employed in glass-making is mined as sandstone, which 



POTTERY. 393 

is crushed preparatory to use. The sands of the United 
States suitable for making the finest grades of glass are 
abundant and found in many of the States. Among the 
beds most extensively worked are those of Berkshire 
County, Mass., Juniata County, Penn., Morgan County, 
W. Va., and some in Illinois and Missouri. 

MAHUFACTUBE OF POTTEBY. 

Pottery in its widest sense includes all articles in which 
clay is the main ingredient and which have been hardened 
by the application of heat, natural or artificial. The 
chemical principles involved in the manufacture of a few 
important kinds will be given. 

The properties of clay which make it the basis of all 
forms of pottery are its plasticity when moist, which 
permits it to be kneaded, and its subsequent hardness when 
heated. The two most general divisions of pottery are the 
glazed and unglazed forms ; of the first, porcelain may 
be taken as the most characteristic variety and highest 
type. 

Porcelain. Porcelain is made from the purest clay or 
kaolin, but a vessel made from clay alone would shrink 
and lose its shape in drying and be liable to crack in the 
kiln. To prevent this, other substances are mixed with the 
clay of the ware, which cause it to retain its form and 
which fuse at the temperature of the furnace, binding the 
whole into a homogeneous compact mass. These fiuxing 
ingredients differ at different manufactories, and to these 
differences are due the various kinds of porcelain. 

In the celebrated Sevres porcelain there is added to the 
kaolin feldspar and a little chalk. In the Meissen por- 
celain there is added feldspar and ground waste-porcelain. 
The other fluxes most commonly used in porcelain are sand, 
bone-ash, and gypsum. In each case the clay and other 
materials are brought to the finest state of subdivision and 



394 APPLICATIONS OF CHEMISTRY. 

usually held suspended in water. The creamy liquids are 
then mixed in the proper proportions, allowed to settle, the 
deposit is separated from the water and the paste thoroughly 
kneaded. The proper proportions of the ingredients may 
be brought together in the dry state and the whole agitated 
together in water. In any case, after the mixed ingredients 
are separated from the water the mass is usually left to 
stand for considerable time, which improves the quality of 
the clay. This result is believed to be brought about by 
the oxidation of any organic matter present and to physical 
change due to drying and shrinkage, which affect the 
plasticity of the clay. When ready for the workman, the 
clay is moulded into the required shape by various forms 
of potters' wheels, jiggers, and lathes, but principally by 
moulds. The most perfect specimens are always finished 
by hand. 

The moulded articles are dried by exposure to the air, 
then packed in cases or saggers and subjected to a com- 
paratively low heat of the kiln. The articles are thus 
sufficiently dried, and hardened to receive the glaze with- 
out danger of breaking. The glaze for the porcelain must 
be similar to the material added for fluxing the clay. 
The glaze for the Sevres porcelain is ground feldspar and 
quartz ; for the Meissen ware it is clay, silica, and ground 
ware. The glaze material is very finely ground and evenly 
applied to the surface of the ware by dusting, or, more gen- 
erally, the glaze is suspended in water and the article is 
deftly dipped into the water and removed. The material 
of the glaze adheres to the surface of the ware. The 
ware is now completely hardened and the glaze fixed 
by exposure, for many hours, to a high temperature ; the 
ware for this purpose is packed in saggers as during the 
preliminary heating. 

The Sevres and Meissen ware come under the head of 
hard porcelain. Porcelain has several characteristics which 



POTTERY. 395 

distinguish it from other forms of glazed ware. The glaze 
is thin and graduates imperceptibly into the body of the 
ware ; the ware is translucent and breaks with a con- 
choidal fracture. Hard porcelain is unique in that the 
ware is subjected to but one burning, the ware being hard- 
ened and the glaze fixed at the same time. 

With all other forms of glazed ware there are two fir- 
ings, one known as the biscuit firing which hardens the 
ware, and the other fixes the glaze upon it. Statue porcelain 
is a true hard porcelain, but is not glazed. 

English soft porcelain is more fusible than. the hard 
porcelain, and the glazing requires a separate firing. 

Stoneware. This is a coarse kind of porcelain made 
from impure material. For glazing, the ware is coated 
with fine sand by dipping it into water holding the im- 
palpable sand in suspension. During the firing of the 
ware damp salt is thrown into the kiln. Decomposi- 
tion ensues, by which hydrochloric acid and sodium 
oxide are formed ; the latter combines with the silica 
and forms sodium silicate, which fuses and constitutes the 
glaze. 

Decorating Porcelain. A uniform color can be given to 
the ware by mixing the proper mineral pigment with the 
glaze. Colors in pattern and design are put upon the ware 
after glazing, and fixed by another firing. 

The most expensive and finest decorating is done by 
hand, but more generally the design is engraved on a cop- 
per plate and a print taken from it in mineral colors on a 
sheet of tissue-paper. By gentle pressure the print ad- 
heres to the ware, and after a short time the paper can be 
removed; the firing then fixes the design. 

The above general description of glazed ware applies to 
that of all countries, but only on the continent of Europe 
is made the hard porcelain by a single firing. In this 
country the white wares suitable for household purposes 



396 APPLICATIONS OF CHEMISTRY. 

may be fitly placed in four grades. The finest is a true 
porcelain, having a vitreous translucent body and a perfect 
accordance between glaze and ware. 

Pottery Kilns. These are solidly built circular structures 
of masonry rising to a crown inside and surmounted by a 
shaft or dome to secure draft. Around the base are the 
fireplaces which open into the kiln. Except for hard 
porcelain the ware is fired twice ; the first is called biscuit 
firing and requires the highest temperature and longest 
time. During this firing the body of the ware is solidified 
into a homogeneous mass, and when withdrawn from the 
kiln and struck it rings almost like metal. The object of 
the second firing is to fuse and fix the glaze, and is known 
as the glost firing. This requires less time and the tem- 
perature is not so high as in the first firing. 

The decorations in design are fixed by a third firing 
which requires less time than either of the other two. 

The porcelain industries in this country are centered at 
East Liverpool, Ohio, and at Trenton, 2s"ew Jersey. The 
Rookwood potteries at Cincinnati are celebrated for their 
special ware, but it is a f ayence or porous ware. The Balti- 
more potteries also produce a porous ware, parian and ma- 
jolica, the latter being quite celebrated. The common forms 
of pottery are produced at many other places in the United 
States. 

Fire-ware. For the manufacture of fire-bricks and such 
articles of pottery as have to withstand a very high tem- 
perature it is of course necessary to employ infusible, ma- 
terial. Nearly pure clay is used for these purposes, to 
which is added a little sand or ground ware, of the same 
description, to prevent shrinkage. Crucibles are also made 
from clay mixed with an equal weight of graphite. Such 
crucibles will withstand rapid changes of temperature with 
impunity. 

Common bricks are made from less pure varieties of 



EXPLOSIVES. 397 

clay which contain sufficient fusible material to clinker the 
bricks during the burning. 

EXPLOSIVES. 

An explosion may in the most general sense be denned as a sudden and 
violent increase in the volume of a substance. In this general sense the 
increase may or may not be due to chemical transformations. This defini- 
tion includes all action by which there may be violent increase of volume; 
thus, a compressed gas or vapor is said to explode, the action being me- 
chanical and the result of the energy originally expended in bringing the 
gas to the compressed condition. In a more purely chemical sense an ex- 
plosion may be defined as a violent increase in the volume of a substance 
brought about by chemical transformations set up in it, resulting in large 
volumes of heated gases. A body capable of undergoing this sudden 
change by chemical transformation upon the application of the proper dis- 
turbing cause is an explosive. 

For our purposes it will only be necessary to describe a few of the more 
important solid and liquid explosives. 

In these explosives the energetic action is due to the rapid conversion 
of a solid or liquid into gases which occupy many times the volume of the 
original substance, the increased volume being due to the change of state 
and to the expansion by heat, resulting from the chemical transformation of 
the explosive. It is evident, therefore, that the energy of the action of an 
explosive will depend largely upon the rapidity of the chemical transforma- 
tion by which it is converted into gas and vapor. The heat of the trans- 
formation, when the products are the same, is independent of the time, 
but the temperature is greater the shorter the time of transformation. In 
the useful explosives the heat liberated and the gases produced in the 
chemical transformation are mainly the result of oxidation processes; the 
bodies oxidized and the oxygen for the purpose all being present in the 
explosives themselves, the oxidation being independent of the oxygen of 
the air. The more important explosives all contain carbon as an essential 
element to be oxidized; other elements are also generally present. We may 
thus conceive explosions to be cases of a special kind of combustion. From 
a purely chemical view, explosives cannot be classified in a definite manner, 
but they may with some convenience be grouped into ex plosive mixtures 
and explosive compounds; these divisions are not entirely distinct nor 
accurate. 



398 APPLICATIONS OF CHEMISTRY. 

PREPARATION OF EXPLOSIVES, 

EXPLOSIVE MIXTURES. 

These consist of a mechanical mixture of two or more 
ingredients which upon the application of the proper dis- 
turbing cause undergo the transformation defined as an 
explosion. 

Simple Explosive Compounds. These are definite chemical 
compounds which from the proper disturbing cause un- 
dergo explosion. 

In such a compound the elements which enter the 
transformed products are all constituents of the single 
original body. In mixtures the elements so entering are 
constituents of the different composing ingredients. 

These simple explosive compounds may be associated 
with other bodies, simple or compound, in such manner as 
to produce modified results in the explosion. The sub- 
stances resulting from such association supply instances of 
explosives which might with equal propriety be classed 
either as mixtures or compounds. The great majority of 
the explosives, however, can be placed in one or the other 
group, bearing in mind the distinction that in explosive 
mixtures the ingredients are in large part capable of 
mechanical separation, and in such explosive compounds 
as contain more than one substance the ingredients cannot 
be so separated. 

Explosives are also sometimes classed as high and low 
explosives ; the former term being applied to those ex- 
plosives in which the transformation is so rapid as to pro- 
duce a rupturing effect, the latter to those in which the 
transformation is less rapid and the effect, in general, one 
of propulsion. 

Explosives are again sometimes classed as explosives of 
the first or second order, depending upon the time in- 



EXPLOSIVES. - 399 

Yolved in the transformation. In explosions of the first 
order the time is very short, the action being practically 
instantaneous ; in the second order the action is much 
slower, the time being appreciable. Explosions of the first 
order are also termed detonations. Every explosive may 
be detonated, and the order of the explosions graduate into 
each other. It is therefore evident that the classification 
just given (into high and low explosives and explosives of 
the first and second order) are without scientific basis, and 
are not more distinctive than the divisions into explosive 
mixtures and explosive compounds. The terms, however, 
have a general significance and are convenient. 

Explosive Mixtures. We have stated that an explosion 
may be considered as a combustion which is accomplished 
independently of the air, by oxygen present in the explo- 
sive. In explosive mixtures some of the ingredients sup- 
ply the oxygen, and the others supply the combustibles for 
oxidation. The most common oxidizing agents in explo- 
sive mixtures are the nitrates and chlorates. These salts 
form the basis for dividing the mixtures into nitrate and 
chlorate mixtures. The former are the more important ; 
the latter are, however, employed to a considerable extent 
in pyrotechny and in igniting other explosives. 

Black Gunpowder. This substance is an intimate mixture 
of nitre, charcoal, and sulphur. It came into extended 
use as an explosive in warfare early in the fourteenth 
century and continued to be universally used until the 
last decade of the nineteenth. Since the latter date its 
use in fire-arms is being largely replaced by different forms 
of smokeless powder. Because of its long career as a 
propelling agent in fire-arms, its composition and the 
chemical principles of its action are herein described. 
The average proportion of the ingredients are usually 
taken as nitre 75 per cent, charcoal 15 per cent, sulphur 



400 APPLICATIONS OF CHEMISTRY. 

10 per cent. Black powder is still largely used in 
pyrotechny. 

Nitre, KNO r This is the oxidizing agent in gunpowder. 
The commercial nitre is always carefully refined before 
incorporation with the other ingredients. The great dif- 
ference in solubility of nitre in hot and cold water is made 
use of in this refining. The impure salt is dissolved in hot 
water, the solution filtered to remove insoluble matter and 
allowed to cool under continual agitation. 

Sulphur. The crude sulphur of commerce is refined by 
distillation, and the distilled sulphur is the variety used in 
the manufacture of gunpowder. It has been pointed out 
that the distilled sulphur belongs to the soluble or electro- 
negative variety, while the sublimed sulphur belongs to the 
electro-positive variety. The first belongs to the same 
electro-chemical group as oxygen, and it is conceivable that 
this fact may explain the difference in properties of the two 
varieties. It is generally thought that the sublimed sul- 
phur from its mode of deposition may contain acid vapors 
in its interstices which would act detrimentally. 

The sulphur for powder should burn without residue, 
and water in which it has been steeped or agitated should 
not show distinct acid properties. 

Sulphur lowers the igniting point of powder, accelerates 
the combustion, increases the temperature of combustion, 
and thereby the volume of gases evolved. It also gives 
permanent solidity to the grain and prevents crumbling to 
dust. 

Charcoal. This is the principal combustible of the pow- 
der. By its oxidation are produced the gases carbon mon- 
oxide and carbon dioxide, with great evolution of heat. 
The charcoals employed result from the destructive distilla- 
tion of several kinds of wood, all of which belong to the 
light woods, as alder, dogwood, and willow. 

The temperature at which the distillation is accom- 



EXPLOSIVES. 401 

piished affects the quality of charcoal. The higher the 
temperature the more nearly pure the charcoal. In general 
it may be said that black charcoal results from tempera- 
tures above 340° C. ; red from temperatures between 300° 
and 340° C. ; and brown below 300° C. 

The higher the temperature at which the charcoal is 
produced the less easily it ignites, but the combustion is 
more rapid after ignition. 

In some powders the percentage of the constituents is different from 
that given above. The cocoa powder contains more nitre and less sulphur. 
The Duponts in this country have made a brown powder in which the sul- 
phur is less, the nitre more, than that given, and a carbohydrate is used to 
replace some of the charcoal. 

Many attempts have been made to replace potassium 
nitrate in black powder, but it has not been successfully 
accomplished. Sodium, ammonium, and barium nitrates 
have all been tried, but the first two are deliquescent, and 
the last is too expensive. In the brown cocoa powder the 
carbon is obtained from rye straw. 

The effects of powder when fired in guns depend both 
upon the composition and the physical texture and struc- 
ture of the powder. These are all varied to meet the 
demands of the military service, and the discussion of these 
subjects does not pertain especially to chemistry. 

Products from the Explosion of Black Gunpowder. The pro- 
ducts from the explosion of powder vary with the con- 
ditions under which the explosion occurs. In general it 
may be said that the oxygen of the nitre combines with 
the carbon, producing carbon monoxide and carbon dioxide. 
A part of the carbon dioxide combines with the potassium, 
forming potassium carbonate. The sulphur is mainly con- 
verted into potassium sulphate. The nitrogen present in 
the powder is liberated. The nitrogen, the carbon mon- 
oxide, and the carbon dioxide expanded by the heat of the 
oxidation account for the explosive effect. The formula 



402 APPLICATIONS OF CHEMISTRY. 

usually assumed to represent the general results of the 
explosion is 

4KJST0 3 + C 4 + S = K,C0 3 + K 2 S0 4 + N 4 + 2C0 2 + CO. 

Besides the products indicated there are always others 
present in small quantity. From the above formula, by the 
consideration of molecular weights, it is seen that solids 
constitute nearly two thirds by weight of the products of 
explosion, and the gases a little over one third. With 
brown, slow-burning powders the proportion of solids is 
less and that of gases more. The smoke from gunpowder 
is due to the solid constituents. 

Gunpowder explodes at 316° G. It can be exploded by 
percussion. 

Chlorate Mixtures. A large number of chlorate mixtures 
has been invented, but none of them has found general 
application as powder. They are mainly used in pyro- 
techny and as fuse mixtures. 

EXPLOSIVE COMPOUNDS. 

It has already been stated that a simple explosive com- 
pound is composed of a single substance. Other explosive 
compounds are composed of more than one substance ; and 
while they are not definite chemical compounds, their in- 
gredients cannot be separated in as simple a manner as in 
the case of explosive mixtures. 

The most important bodies which are classed as explo- 
sive compounds are the nitro-explosives, or those explosives 
associated with other substances or with each other. In 
the nitro-explosives there is present as a constituent in the 
molecules an NO. z group, which supplies the oxygen in- 
volved in the chemical transformations of the explosive. 
This ]N"0 2 group is introduced into the exj^losive by the 
action of nitric acid upon a hydrocarbon or a hydrocarbon 
derivative. 



EXPLOSIVES. 403 

The most important of the nitro-explosives are the 
nitro- compounds and the organic nitrates. The most 
important gronp of the nitro-componnds are those result- 
ing from the action of nitric acid npon the benzene hydro- 
carbons. Mtro-glycerine and gun-cotton are the most im- 
portant examples of organic nitrates. Gun-cotton was 
formerly thought to be a nitro-substitution compound, but 
it is now classed among the organic nitrates. Nitro-glyce- 
rine is an ethereal salt of nitric acid. 

All these classes are produced by the action of nitric 
acid upon hydrocarbon derivatives, and in each case the 
resulting molecular change consists in the substitution of 
one or more groups of N0 2 for one or more atoms of 
hydrogen in the derivative. The precise distinction be- 
tween substitution compounds and organic salts will be 
stated after we have described some of the bodies. We, 
may without any inconvenience consider the classes named 
as derived by the replacement of one or more hydrogen 
atoms by one or more groups of N0 2 . We shall first de- 
scribe the two principal organic nitrates and some of their 
derivatives. 

NITRO-GLYCERINE OR NITRIC GLYCERIDE. 

Mtro-glycerine is prepared by the action of a mixture 
of strong nitric and sulphuric acids upon glycerine. The 
function of the sulphuric acid seems to be to preserve the 
strength of the nitric acid by combining with the water 
liberated during the transformation of the glycerine. The 
reaction for the conversion is represented by 

C 3 H 8 3 + 3HN0 3 = C 3 H r A(NO,\, + 3ILO. 

It is prepared by gradually adding glycerine to a mixture 
of strong nitric and sulphuric acids, the best proportions 
being three of nitric to five of sulphuric by weight, both 
acids being of great strength. 



404 APPLICATIONS OF CHEMISTRY. 

Properties of Mtro-glycerine. Nitroglycerine is a heavy 
oily liquid of specific gravity 1.6 at 15° C. When pure it 
is white, without odor, but the commercial product is 
usually pale yellow. It is poisonous when taken internally. 
It is insoluble in water, soluble in ether, benzene, and 
methyl-alcohol; it is less soluble in ethyl- than in methyl- 
alcohol. When x^ure it has been kept ten years without 
deterioration. It solidifies at about 8° C, though the 
freezing-point varies with the quality of the nitro-glycerine. 
In the solid form it is much less sensitive than in the liquid 
state. 

Nitro-glycerine explodes by concussion. If a small 
quantity of it be ignited it will burn away without explo- 
sion. In a confined space it explodes when heated up to 
180° C, though in small quantity it has been heated to a 
higher temperature without explosion. Mtro-glycerine 
which has not been thoroughly freed from acids or when 
subjected to too high a temperature is liable to become 
dangerous from spontaneous decomposition. It can be 
detonated by means of mercuric fulminate. 

The products of the explosion of nitro-glycerine are 
shown by the reaction 

2C 3 H 5 (N0 3 )3 (exploded) = 5H 2 + 6C0 2 + O + 6N. 

The temperature of combustion or calorific intensity of 
nitro-glycerine, that is, the temperature to which its heat 
of combustion would raise the products, is 3005° C, accord- 
ing to Yuick. The gaseous products from the explosion of 
nitro-glycerine are about 1500 times the volume of the ex- 
plosive taken at 15° C, the gases being measured at the 
temperature of 100° C. and under atmospheric pressure. 

Owing to the dangerous nature of liquid nitro-glycerine, 
its use in this form has long since been abandoned in 
Europe, and it is not now generally used in this country. 

Nitro-glycerine Derivatives. To overcome the objections 



EXPLOSIVES. 405 

to the liquid form, many explosives of which it is the basis 
have been tried. These derivatives of nitro-glycerine may 
be grouped into two classes : 1st. When nitro-glycerine is 
associated with a chemically inert substance ; 2d. When 
with a substance that takes chemical part in the explosion. 

The most important of the first group is common dyna- 
mite, usually termed dynamite No. 1. It consists of nitro- 
glycerine absorbed by a porous siliceous earth which is 
mainly composed of the shells of diatomacese. The better 
forms of this earth will absorb three times their weights of 
nitro-glycerine. The earth serves merely to give solid form 
to the explosive. 

To the second class belongs a large number of explosives 
consisting of nitro-glycerine associated with chemically 
active substances. Charcoal and charred sawdust are used 
to absorb it, and it is mixed with gunpowder and other ni- 
trate and chlorate mixtures. Mtro-glycerine is also mixed 
with other nitro-explosives, some of which will be men- 
tioned later. 

The objects aimed at in associating other substances 
with nitro-glycerine are to get it in less dangerous form 
than the liquid, and at the same time to increase its effect 
by using as auxiliary substances bodies capable of combin- 
ing with the free oxygen known to be present in the gases 
resulting from the explosion of nitro-glycerine alone. 

GUN-CQTTON, PYROXYLIN. 

This body is the nitrate of cellulose and results from the 
action of strong nitric acid upon cellulose. The N0 2 groups 
of the acid replace the corresponding number of hydrogen 
atoms in the cellulose. We have given the formula of cellu- 
lose as (C 6 H 10 O 5 ) n , which maybe written (C G H 10 O 5 ) 2 or dsH^Ojo. 
Using this formula, the reaction for the production of gun- 
cotton is 

C 12 H w 4 (OH\ + 6(HO,N0 2 ) - C 12 H 14 4 (0,lSr0 2 ) 6 + 6H 2 0. 



406 APPLICATIONS OF CHEMISTRY. 

Gnn-cotton is a hexanitrate, six atoms of hydrogen being 
replaced by six molecules of N0 2 . Not forgetting that its 
actual formula is a hexanitrate. its production for con- 
venience may be represented thus : 

CH,A - 3HX0 3 = 6 H 7 O 5 (NO 2 ) 3 + 3H z O, 

making it similar to that for the production of nitro- 
glycerine. 

Gun-cotton like nitro-glycerine is prepared by the action 
of a cold mixture of strong nitric acid and sulphuric acid 
upon cellulose. The sulphuric acid serves the same pur- 
pose as in the manufacture of nitro-glycerine. The cotton 
is perfectly freed from all grease and oil. It is next opened 
up by carding and cutting into short fibres. It is then 
ready for treatment with the acids, after which it has to be 
thoroughly washed to remove free acid. After washing. 
the cotton is now generally converted into a pulp by a 
machine similar to a rag-engine in a paper-mill. It is then 
subjected to a final washing to remove every trace of the 
acid, drained and moulded into blocks, disks, and other 
forms that maybe required. The gun-cotton is now seldom 
employed in the form of cotton wool. 

From the chemical change indicated in the reaction it 
is seen that the cotton increases greatly in weight. In 
England, from motives of economy, cotton waste is the 
material used for the conversion into gun-cotton. 

Properties of Gun-cotton. Gun-cotton wool cannot be dis- 
tinguished from the raw cotton by the eye. It is harsher 
to the touch. It dissolves in acetic ether and acetone. If 
ignited when loose in the air. it flashes with a yellow flame. 
It can be exploded by a blow, but generally only the par- 
ticles struck explode. Fully nitrated cotton has often been 
heated rapidly to 180° C. without explosion, but it is very 
risky to heat it above 175° C, and it often explodes below 
this. 



EXPLOSIVES. 407 

Ignited in a confined space the burning of the first por- 
tion raises the remainder to the temperature of explosion. 
Either dry or wet gun-cotton may be detonated by fulmi- 
nate. Both nitroglycerine and gun-cotton will undergo 
sympathetic detonation; that is, the detonation can be com- 
municated along a row of cartridges of either of these ex- 
plosives, though not in contact, when one of them is ex- 
ploded. Gun-cotton like nitro-glycerine may be detonated 
Tinder water. 

The products of the explosion of gun-cotton vary some- 
what with the conditions of the explosion, but when per- 
fectly detonated they may be expressed by the reaction 

2C 6 H T 5 (N0 2 ) 3 = 7H 2 + 3C0 2 + 9CO + 6N, 

which shows that it does not contain sufficient oxygen for 
the complete combustion of the carbon. All the products 
being gaseous as in nitro-glycerine, there is no smoke. In 
mining operations the absence of smoke is advantageous, 
but the effects of the carbon monoxide produced are detri- 
mental. By associating the gun-cotton with some oxidizing 
agent the effect of the explosion may be increased and the 
carbon monoxide converted into carbon dioxide ; thus for 
many purposes some nitrate is often associated with the 
gun-cotton. 

Collodion Cotton; Soluble Pyroxylin. The common gun- 
cotton just described is a hexanitrate and is insoluble in a 
mixture of alcohol and ether. The collodion cotton is a 
mixture of several lower nitrates, and is soluble in the 
alcohol and ether mixture. It is made by the action of 
weaker nitric and sulphuric acids upon the cotton. It is 
less explosive than gun-cotton, but is largely manufactured 
Hor preparation of celluloid, smokeless powder, and gelatine 
explosives. 

Gelatine Explosives. It has been seen that gun-cotton 
contains too little oxygen for the complete combustion of 



408 APPLICATION'S OF CHEMISTRY. 

its carbon. As collodion cotton is composed of lower ni- 
trates, it contains still less in proportion to the carbon. The 
deficiency of the oxygen in the gnn-cotton can be supplied 
by associating it with other substances, and this is done in 
the gelatine explosives. 

The simplest and one of the most important of the gela- 
tine explosives is blasting gelatine. This consists of about 
seven parts of collodion cotton dissolved in about ninety- 
three parts of nitro-glycerine. The excess of oxygen in 
the latter strppties the deficiency of that element in the 
former. This explosive is more powerful than either of 
its constituents. Its sensitiveness may be increased by the 
addition of a little gun-cotton and decreased by the addi- 
tion of a little camphor. 

Blasting gelatine is an amber-colored soft elastic mass, 
which can be bent without permanently losing its shape. 

Gelatine Dynamite. To diminish the violence of blasting 
gelatine, it is sometimes thickened with other ingredients, 
the nitro-glycerine in the gelatine being diminished. Gela- 
tine dynamite and gelignite consist of the same ingredients 
as blasting gelatine in different proportions, incorporated 
with potassium nitrate and wood-pulp. 

Celluloid. This substance is not classed as an explosive, 
though masses of it have been known to explode. It is 
composed of collodion cotton and a large percentage of 
camphor. The proportions usually employed are two 
parts of collodion cotton and one part of camphor. 
Celluloid appears to be a mechanical mixture, the camphor 
being capable of extraction by proper solvents. Cellulose 
from tissue-paper is generally used in making celluloid. 

Xylonite and artificial ivory are forms of celluloid. 

NITRO-EXPLOSIVES FROM THE BENZEXE GROUP. 

Nitro-compounds. As already stated, the nitro-explosives 
from the benzene derivatives are nitro-substitution com- 



EXPLOSIVES. 409> 

pounds as distinguished from organic nitrates. The dis- 
tinction between the two classes will be referred to later, but, 
as stated, for our purposes both classes may be assumed 
to be formed in the same way, that is, by the replacement 
of one or more atoms of hydrogen in the hydrocarbon 
by one or more groups of N0 2 . 

Nitro-compounds of Benzene. By the action of nitric acid 
upon benzene three nitro-benzenes may be produced, mono-, 
di-, and tri-nitro-benzenes, C 6 H 5 ]N"0 2 , C 6 H 4 (N~0 2 ) 2 , and 
C 6 H 3 (]Sr0 2 )3. The first two are not explosive in themselves, 
but are associated with other substances in the preparation 
of certain explosives. Tri-nitro-benzene is said to be ex- 
plosive, though it has not yet been used as such. The 
nitro-benzenes need not therefore be here considered as 
explosives. Mono-nitro-benzene is largely used to prepare 
aniline, from which is obtained a host of beautiful dyes. 

Tri-nitro-phenol ; Picric Acid. This is an important nitro- 
compound from the benzene derivative, phenol. It is ob- 
tained by the nitration of phenol, carbolic acid, C 6 H 5 OH. 

The action of nitric acid upon phenol may be repre- 
sented by the equation 

C 6 H 5 OH + 3(HO,N0 2 ) = C 6 H 2 (N0 2 ) 3 OH + 3H 2 0. 

Picric acid is explosive and is used to a limited extent 
as such, but the acid is far more important because of the 
salts it produces, which are more stable than the acid and 
very explosive. 

It may be said that the nitro- compounds from the ben- 
zene group are not much used alone as explosives, but they 
are all used as auxiliaries in the preparation of explosives. 
It will be possible to mention only a few of the important 
examples. 

Rack-a-Rock, the explosive used in the great explosion at Flood Rock 
(Hell Gate), New York, consisted of mono-nitro-benzene absorbed by 
potassium chlorate. 



410 APPLICATIONS OF CHEMISTBY. 

Bellite. This is a mixture of ammonium nitrate and di-nitro-benzene. 

Several military powders have been made which consist of mixtures of 
ammonium and potassium picrates with nitre or with nitre and charcoal. 

Nitro-compounds and Organic Nitrates. The distinction between a 
nitro-compound or substitution product and a nitro-ether or ethereal salt 
is based upon the transformations they undergo when subjected to the 
action of certain reagents. From this basis, the N0 2 group which is 
present in both classes is believed to be differently attached in the 
molecule. Some of the nitro-compounds have the same molecular 
formulae as certain nitro-ethers, but they are found to be metameric 
bodies and not isomeric ; thus the ether salt, 2 H 5 ONO (ethyl nitrite), 
is metameric with the substitution compound nitro-ethane, C 2 H 5 N0 2 . 
The reactions which the two classes undergo justify the belief that the 
hydrocarbon radical is connected to the nitroxyl group through the N atom 
in the substitution compound, and through an atom in the ethereal salt. 
There is also reason for thinking that the mode of formation of the two 
classes is different. This difference can be better understood by an illustra- 
tion. The nitro-compound C 6 H 5 N0 2 (nitro-benzene) may be considered as 
produced by the action C 6 H 5 ,H (benzene) + HO,N0 2 = C 6 H 5 N0 2 + H 2 0, 
in which either the N0 2 replaces the H of the benzene or the C 6 H 5 replaces 
the OH of the acid. Nitro-glycerine, the nitric ether of glycerine, is an 
ethereal salt of nitric acid resulting from the replacement of the hydrogen 
of the acid by the basic alcohol radical of glycerine, 

C 3 H 5 (OH) 3 + 3(OH,N0 2 ) = C 3 H 5 (0,M) 2 ) 3 + 3H 2 0. 

In this the trivalent radical C 3 H 5 replaces three atoms of hydrogen, or 
the acid radical N0 2 replaces the hydroxyl hydrogen of the alcohol. 
Considering the hydrocarbon radical in the two cases, it is seen that in 
nitro-benzene the radical has replaced OH, in the nitro-glycerine it has 
replaced H. All ethereal salts may be considered as formed in this way, 
by the replacement of the hydrogen in the acid by the alcohol radicals. 

These ethereal salts are also called esters, and the distinction between 
the constitutional formulas of these and nitro-compounds may be generally 
represented by E — N0 2 and K — O — M) 2 , in which E stands for a hydro- 
carbon radical, the N atoms being directly connected with the radical in 
the compounds, and through O atoms in the ethers. 

Gun-cotton was formerly classed as a nitro-compound, but it is now 
thought to be an organic nitrate, cellulose nitrate.. This conclusion is 
reached from the fact that under the action of reagents its reduction 
products place it among the organic nitrates rather than among the nitro- 
substitution compounds. 



EXPLOSIVES. 411 

SMOKELESS POWDERS. 

It was natural that in the first efforts to prepare a 
smokeless powder as a propelling agent it should have been 
attempted to use some of the known high explosives which 
left no solid residue in exploding. Many attempts were 
made to adapt gun-cotton to this purpose, as it was thought 
to promise most favorable results. These early attempts 
were all mainly based on a purely physical manipulation 
of the cotton wool and resulted in failure. 

The smokeless powders of the present day may be 
grouped into three general classes : 1st. Those in which 
the only explosive used is some form of nitro-cotton; 2d. 
Those in which nitro-glycerine and some form of nitro- 
cotton are used; 3d. Those in which nitro-derivatives of 
benzene alone or with nitro-cellulose are used. 

The more important and successful powders belong to 
the first class. 

The first class includes a number of powders made by 
kneading the nitro-cotton in a proper solvent and bringing 
it to such a consistency that it can be rolled into tenacious 
sheets, after which it is cut into flakes. These powders are 
known as flake powders, and are largely made in several 
European countries. By a little different manipulation the 
kneaded mass is converted into grains and gives granulated 
powder. The solvents used are acetic ethers or acetones. 
These powders sometimes contain some additional sub- 
stance to retard their action when ignited, but by careful 
manipulation they are now made without such addition. 
The effect of the solvent and the physical treatment pro- 
duce the desired result. Some of the powders are glazed, 
which has a retarding effect upon their explosion. 

The second class includes a number of noted powders 
made by dissolving collodion cotton in nitro-glycerine, or 
gun-cotton in nitro-glycerine and acetone. In these pow- 



412 APPLICATIONS OF CHEMISTRY. 

ders the ingredients are kneaded or thoroughly mixed 
together and may be then rolled into sheets or cut into 
flakes, or may be pressed through small cylindrical open- 
ings into cords or fibres. Ballistite, cordite, and the 
American Leonard and Peyton powders fall into this 
class. Each of these powders contains a small addition of 
certain other substances for decreasing rapidity of action. 

The third class includes a number of powders resulting 
from associating picric acid or the picrates with other sub 
stances. The picrates of potassium and ammonium are 
employed. A number of such powders has been invented, 
but none has proved very successful or come into general 
use. One of the American smokeless powders by the 
Duponts is also made by dissolving nitro-cellulose in ben- 
zene. As already stated, the last class is of little import- 
ance compared with the other two. 

The number of explosives and powders is entirely too 
great to be here described or even mentioned. The physi- 
cal manipulation involved in their preparation does not 
properly belong here, and only their general chemical rela- 
tions have been referred to. 

FULMINATES. 

The fulminates are the salts of fulminic acid. The acid has not been 
isolated, but its formula is assumed to be Ca^OaHa. The principal salts of 
this acid are the fulminates of mercury and silver ; the other metallic ful- 
minates are obtained from these. 

The most important is that of mercury, commonly known as fulminating 
mercury. This fulminate is prepared by dissolving mercury in nitric acid 
and acting upon it with alcohol; its formula is CaNaOaHg. 

It is a white solid when pure, but is usually of a gray color. It is ex- 
tremely sensitive to explosion, and detonates by percussion, by heat (187° C.) r 
by the electric spark, or by contact with nitric or sulphuric acid. Its 
explosion is represented by the reaction 

HgC 3 N a 2 (exploded) = Hg + 2CO + N 9 . 

It is used mainly to detonate other explosives. For this purpose it is 
employed either singly or with other substances. Potassium chlorate,. 



ILLUMINATING GAS. 413 

nitrate, meal powder, and antimony sulphide are some of the common 
substances used with it, 

The fulminate or the fulminating mixture is enclosed in thin metallic 
cylinders for use as detonators. 

It will be observed that mercuric fulminate contains an N0 2 group, and 
a hydrocarbon derivative (alcohol) is employed in its preparation, though 
it does not contain hydrogen. The rational formula of the body has not 
yet been agreed upon. 

ILLUMINATING GAS. 

COAL-GAS. 

The idea of preparing an illuminating gas from coal 
seems to have become first well defined in the mind of Wil- 
liam Murdoch, a Scotchman, in 1792. In this year he 
lighted his house with coal-gas. By the year 1800 he had 
extended the use of the new illuminant to all the principal 
shops and foundries near Birmingham. Murdoch's inven- 
tion did not become known on the continent of Europe until 
the beginning of the nineteenth century. The French claim 
the invention for their countryman Lebon, who in 1801 illu- 
minated his house with gas from wood. Gas lighting was 
first introduced into the streets of London in 1807, and had 
Tbecome general by 1814. Paris was lighted by gas in 1820, 
and after this date the use of gas rapidly spread over 
Europe. The manufacture of gas has ever since been an 
industry of great extent and magnitude. The gas generally 
designated as coal-gas and used for illuminating purposes 
is a mechanical mixture of a number of permanent gases, 
some of which are luminous, while others produce little light 
when separately burned. There are also present the vapors 
of many substances which greatly add to the light-giving 
power of the gas. Coal-gas is generally manufactured by 
the destructive distillation of bituminous coal. 

Bituminous coal is essentially composed of carbon, hy- 
drogen, oxygen, nitrogen, sulphur, and a little mineral 
matter. In general the carbon amounts to about seventy- 



414 



APPLICATIONS OF CHEMISTRY. 



five per cent of the coal. When bituminous coal is subjected 
to the action of heat out of contact with air there results a 
large number of compounds composed of two or more ele- 
ments of the coal. There have already been distinguished 
nearly a hundred bodies among the products of the distilla- 
tion of coal. It is evident from this fact that coal is a com- 
plex body. The original arrangement of the elements in 
the coal has not been determined, but it is certain that the 
numerous distillation products are not primary constituents 
of the coal, but result from the application of heat. They 
are products of the distillation and not mere educts from 
the coal. 



COAL-GAS MANUFACTURE. 



Retorts. In the manufacture, bituminous coal is placed 
in fire-clay retorts capable of being hermetically sealed. 
The retorts, i?, are generally D- shaped cylinders about ten 




Fig. 16. 

feet long and from fourteen to twenty inches in diameter. 
The charge of coal is usually from two hundred to four 
hundred pounds and remains in the retort from four to six 
hours. The coal is always introduced into a heated retort. 
The retorts are arranged in benches so that a number can 
be heated by the same furnace, and they are kept above a 
red heat. During the heating the volatile products of the 
distillation are driven off and coke is left in the retorts. 



ILLUMINATING GAS. 415 

The principal products of the distillation which pass 
from the retorts are vaporized liquid hydrocarbons, water- 
vapor, hydrogen, marsh gas, acetylene, defiant gas, am- 
monia, hydrogen sulphide, carbon dioxide, carbon mon- 
oxide, cyanogen, nitrogen, and carbon disulphide. 

Ascension Pipe and Hydraulic Main. From the front 
Upper surface of each retort rises an iron pipe. These pipes 
extend upward and then curve down and enter a large iron, 
cylinder called the liydraullc main, which runs perpen- 
'dicular to and above the retorts and receives the pipes 
from all the retorts. The pipes are called ascension pipes, 
and are shown at A. 

The hydraulic main is kept partially full of water and 
other condensed liquid products of distillation. The ends 
of the ascension pipes dip beneath the liquid in the main. 
A portion of the heavy hydrocarbon vapors and nearly all 
of the aqueous vapor are condensed in the hydraulic main. 
The former constitutes tar ; the condensed aqueous vapor 
takes up ammonia, carbon dioxide, hydrogen sulphide, and 
cyanogen, forming what is known as the ammoniacal 
liquor. 

The gases and more volatile products of the distillation 
bubble up through the liquid in the main. This liquid 
acts as a seal to prevent the gases from returning to the 
ascension pipes when the retorts are open for recharging. 

Condensers. From the hydraulic main the uncondensed 
products are carried by an iron pipe, F, called the foul main, 
to the condensers. The condensers, (7, are a series of pipes 
through which the gas passes and which furnish a large 
cooling surface ; the condensers may be cooled by running 
water or simply by exposure to the air. In the condensers 
are deposited the liquid hydrocarbons (tar), ammoniacal 
salts, and aqueous vapor which have passed through the 
hydraulic main. The condensed products are conducted 
by pipes to suitable receptacles for removal. 



416 APPLICATIONS OF CHEMISTRY. 

Exhausters. Immediately after the condensers, exhaust- 
ers are usually placed. The exhauster, PJ, is a form of pump 
for pulling the gas away from the retort and forcing it 
through the subsequent parts of the plant into the holder. 
If it were not for the exhauster the pressure of the gas in 
the retorts would have to be sufficient to overcome all the 
resistances in the different parts of the plant and thus 
cause loss of gas by leakage in the retorts. 

Washers and Scrubbers. From the exhausters the gas 
passes through the washers and scrubbers or through 
scrubbers alone. The washers are arrangements in which 
the gas is made to traverse thin layers of liquid. In scrub- 
bers the gas is not forced to pass through the water, but is 
brought into intimate contact with wetted surfaces. A 
common form of scrubber, 8, is a cylinder filled with coke 
over which water continually trickles. In the passage 
through the washers and scrubbers the remaining ammonia 
and some of the hydrogen sulphide and carbon dioxide are 
removed. The scrubbers are sometimes placed in front of 
the exhausters. 

Purifiers. From the scrubbers the gas passes through 
the purifiers, P, the object of which is to remove the remain- 
ing hydrogen sulphide and carbon dioxide from the gas. 
The purifiers are generally square iron boxes, divided by a 
number of horizontal sieves. The purifying material is 
placed in layers upon these sieves, and the gas is made to 
traverse the several layers before leaving the purifiers. 

The materials used in the purifiers are slaked lime or 
iron oxide, either separately or in succession. The slaked 
lime takes out both hydrogen sulphide and carbon dioxide, 
while the iron oxide removes only the hydrogen sulphide. 
The carbon dioxide diminishes the illuminating power of 
the gas, and when not removed, the illuminating power can 
only be kept up by enriching the gas in a manner yet to be 
explained. 



ILLUMINATING GAS. 417 

The great advantage of the iron oxide is that its purify- 
ing power can be restored a number of times by simply 
exposing it to the atmosphere. The lime cannot be used 
again, and cannot be economically used except where it is 
very cheap and can be readily disposed of when spent. If 
the substances are used in succession, it is better to pass the 
gas through the iron oxide first and then through the lime. 
When. lime is employed as the purifying agent calcium 
sulphide and calcium carbonate are produced ; when iron 
oxide is employed the mono- and sesqui-sulphides of iron 
are produced. When these sulphides are exposed to the 
air the iron oxide is reproduced and the sulphur deposited. 
The oxide may thus be repeatedly revivified until the 
separated sulphur amounts to fifty-five per cent. Purifica- 
tion by iron oxide alone is the method now generally 
employed. 

The reactions in the iron purifiers are 

Fe 2 3 + 3H 2 S = Fe 2 S 3 + 3H 2 ; 
Fe a O, + 3H,S = 2FeS + S + 3H 2 0. 

The oxide is reproduced by exposure to the air and the 
reactions are 

2FeS + 3 = Fe 2 3 + S 2 and Fe 2 S 3 + 3 = Fe 2 3 + 3S. 
The oxide of iron used may be a natural product, bog iron- 
ore, or it may be artificially prepared by the oxidation of 
iron borings or filings. In this country the oxide is very 
generally prepared from the material just named. 

Carbon disulphide, when present, is one of the most 
difficult impurities to remove from the gas, and there is 
demanded for this result special provision not deemed 
necessary for description here. 

The Gasometers. From the purifiers the gas passes to the 
holders or gasometers, and is there stored for use, and dis- 
tributed as required to consumers. 

The composition of purified coal gas differs at different 



418 APPLICATIONS OF CHEMISTRY. 

places ; in general it may be stated that the composition is 
approximately H = 50 per cent ; saturated hydrocarbons of 
the paraffin series, mainly marsh gas = 30 to 40 per cent ; 
unsaturated hydrocarbons, mainly benzene, acetylene, and 
ethene, 3 to 5 per cent ; nitrogen, 3 to 5 per cent ; carbon 
monoxide, 3 to 5 per cent, with small quantities of oxygen 
and carbon dioxide. 

The luminosity of the gas is believed to be due to the 
combined action of the hydrocarbons and can in no great 
degree be attributed to any one of them alone. The quality 
of the gas is of course affected by the temperature of the 
distillation. At too low a temperature the solid and liquid 
hydrocarbons are too abundant ; at too high a temperature 
the gaseous hydrocarbons are decomposed, carbon being 
deposited as gas carbon and hydrogen being liberated. 

The illuminating power of gas from common coal was 
formerly generally increased by adding to the charge of 
the retort a small quantity of cannel coal. This result is 
now frequently brought about by impregnating the gas 
with vapor of the volatile hydrocarbons. This is often done 
in this country by introducing into the retort a small iron 
cylinder (called cartridge) containing paraffin oil obtained 
from petroleum, the cartridge being loosely closed. 

Secondary Products from Coal-gas Manufacture. The 
secondary products from the gas manufacture are numerous 
and important. The hydraulic main, the condensers, and 
the scrubber have until recently been the source of nearly 
all the ammoniacal salts of commerce. The coal tar by dis- 
tillation readily yields two portions, the light and heavy oil. 
From the light oil naphtha, benzene, toluene, and other less 
important bodies are obtained ; from the heavy oil naph- 
thalene and carbolic acid are obtained. Besides the bodies 
named there are many others of great theoretical impor- 
tance to organic chemistry. These secondary products are 
now obtained in considerable quantity from other sources. 



ILLUMINATING GAS. 419 

Carburetted Water-gas. — The production of water-gas was 
referred to under the discussion of carbon monoxide. As 
neither of the constituents (carbon monoxide and hydro- 
gen) of this gas gives much light, it must be enriched before 
use as an illuminant. This is accomplished by mixing with 
the water-gas, hydrocarbons obtained from the decomposi- 
tion of petroleum oils. 

The enriched or carburetted form is now largely used, 
especially in the United States, as an illuminating agent. Its 
manufacture in this country has assumed very large propor- 
tions. There have been tried various forms of generators, 
but the essential parts of those most generally employed at 
the present time are very similar. The Lowe and Humphrey 
plants are in most general use in America. The essential 
parts of such gas plant are the generators and superheaters. 
The generators are cylindrical furnaces lined with fire- 
brick. In the generators the fuel, usually coke or anthra- 
cite, is heated to incandescence by an air blast, a portion 
of the fuel being consumed in the process. The resulting 
gas, called "producer gas," containing a large amount of 
carbon monoxide, is led into the superheaters, enough air 
being admitted to insure the combustion of the CO. The 
superheaters are also cylindrical furnaces charged with a 
checkerwork of brick so as to expose a large surface to 
the producer gas. By continuing the air blast sufficiently 
long the fuel in the generators and the fire-brick in the 
superheaters are raised to a high temperature (white heat). 
The air blast is then turned off and steam blown through 
the generator. The steam is decomposed by the heated 
carbon, forming water gas in accordance with the equation 

C + H,0 - CO + EL 

The water-gas, at the top of the generator, meets a spray 
of crude petroleum and carries the volatilized products into 
the superheater. Here the contact of the volatilized prod- 



420 APPLICATIONS OF CHEMISTRY. 

ucts with the highly heated bricks changes the oil vapors 
into permanent gases and they pass on as constituents of 
the enriched water-gas. When the temperature of the fuel 
in the generators falls too low for action, the steam is 
turned off and the air blast turned on again and the opera- 
tion repeated. The action is intermittent. 

Water-gas is valuable as a heat producer, and for this 
purpose does not need to be carburetted. Its flame is en- 
tirely free from smoke and comparatively so from sulphur 
compounds. It produces a high temperature and a clear 
heat, and is very efficient in melting and welding metals 
and in porcelain and glass manufacture. 

ALCOHOLIC BEVERAGES. 

The different alcoholic beverages of mankind may be 
grouped into two classes: 1st, fermented ; 2d, distilled. 
The fermented may be divided into the less general classes, 
beers and wines. These classes, with the general principles 
of their production, will be briefly described. 

Fermented Liquors. Beers and Wines. Beers are the 
products of fermentation of glucose which has been directly 
produced by the transformation of starchy substances. 
Wines are the products of the fermentation of glucose 
existing as such in the fruits used. 

BEER-MAKING. 

Malting. Beer is generally producd from barley. In 
the operation of malting, the grain is first soaked in water 
until it has swollen and become soft. It is then spread in 
layers, under the proper conditions for germination, in a 
dark place kept at a constant and moderate temperature. 
Under these conditions the grain sprouts, and when the 
radicle or sprout has grown to about half an inch the 
vitality of the grain is destroyed by kiln- drying and the 



ALCOHOLIC BEVERAGES. 421 

radicle made brittle by the final temperature, to which it is 
subjected, so that it is easily broken off and can be removed 
by sifting. The radicle is valuable as a manure, as it contains 
about one ninth the nitrogen of the grain. 

During the germination the seed absorbs oxygen, gives 
off carbon dioxide, and there is produced a substance 
known as diastase ; this converts some of the starch into 
dextrin and glucose, which serve as food for the developing 
radicle. Diastase contains carbon, hydrogen, oxygen, and 
nitrogen, but its formula is not known. The malted grain 
contains about one fifth of one per cent of its weight of 
diastase, perhaps a little more. 

Brewing. Preliminary to brewing the malted grain is 
ground to an even grist and infused in water at the tempera- 
ture of about 77° C, where it is left for several hours, during 
which the diastase acts upon the unaltered starch and con- 
verts the greater portion of it into sugar and dextrin. The 
water with its dissolved constituents is called wort. It is 
drawn off from the exhausted malt and run into a wort- 
boiler. The exhausted malt contains some starch and nitro- 
genous matter and is used as food for animals. 

The wort is next boiled with the requisite quantity of 
hops. The flowers of hops contain a bitter principle called 
lupulin and an essential oil. They confer upon the beer 
its aromatic flavor and odor and tend to prevent the con- 
version of the alcohol into acetic acid. The boiling also 
effects the removal of a considerable quantity of nitro- 
genous matter resulting from the gluten of the grain, which 
matter would be deleterious to the keeping properties. 

After boiling with the hops the wort is drawn off and 
cooled rapidly to about 15° C, to avoid the action of the 
air in producing acid fermentation which occurs if cooled 
slowly. The wort is then transferred to the fermenting 
vessels or tuns and made to ferment by the addition of the 
proper quantity of yeast. 



422 APPLICATIONS OF CHEMISTRY. 

Yeast is a vegetable micro-organism (already referred to) 
which possesses the power of converting sugar into alcohol 
and carbon dioxide. It is also capable of inducing the con- 
version of cane sugar into glucose. 

The fermentation is the most important part of the opera- 
tion of brewing. The process is controlled by attention to 
the temperature of the liquid and the general appearance of 
the tuns. The extent to which the fermentation has pro- 
ceeded can be well determined by the density of the wort. 
The yeast is always removed before the fermentation is 
completed and the beer drawn off into casks, where it 
undergoes a slow fermentation and becomes charged with 
carbon dioxide. 

Besides the water, alcohol, and carbon dioxide, the 
finished beer contains some unchanged glucose and dextrin, 
the extract from the hop, some nitrogenous matter from the 
grain, and the soluble mineral matter of the grain except 
the phosphates, which are consumed by the yeast. There 
are present in small quantity other secondary products of 
the fermentation, as acetic acid, glycerin, etc. 

Porter, stout, and highly colored beer are made by 
having a small quantity of the malt strongly dried or 
charred so as to convert some of the sugar into caramel. 
The amount of alcohol in beers varies from two to nine per 
cent. 

The beer yeast if deprived of moisture by drying at a 
low temperature, or by pressure, can be kept for a long 
time without losing its powers, but if heated to 100° C. it is 
killed and is no longer capable of producing fermentation. 

The yeast plant grows and increases at the expense of 
phosphates and nitrogenous matter of the wort, these being 
necessary to its growth. As previously stated it is during 
the growth of the yeast that fermentation takes place. In 
a solution of pure sugar the yeast will transform only a 
limited quantity of the sugar and is destroyed by the action. 



ALCOHOLIC BEVERAGES. 423 

WITNTE- MAKING. 

We have stated that wines result from the fermentation 
of the glucose existing in the fruits from which the wine is 
made. The term is generally applied only to those bever- 
ages made from grapes. Wine further differs from beer in 
that the maker adds no ferment. The expressed juice of 
the grape undergoes spontaneous fermentation. This fer- 
mentation is due to the fact that the yeast spores are gen- 
erally present on the skin and stalks of the grape and are 
carried about by the air. The grape juice contains the 
necessary constituents for the sustenance of the yeast, and 
when the yeast spores are deposited in it they readily 
grow, the vinous fermentation resulting. If all the sugar 
be fermented the wines are said to be dry, otherwise the 
wine remains sweet. 

The skins, stalks, and seeds of the grape contain tannic 
acid and several coloring matters. The color and slightly 
astringent taste of the red wines are due to the fact that 
the skins are left for a certain time in the fermenting juice, 
and the alcohol produced dissolves out the tannic acid and 
the coloring matter. In white wine the fermentation does 
not take place in contact with the skins. Red wines are 
generally fermented in vats, white wines in casks. 

After fermentation the wines are decanted and very 
frequently clarified. Red wines are usually clarified by 
albumen, while the white are clarified by gelatin (isin- 
glass). The action of the albumen .or gelatin is purely 
mechanical. The tannin in the wine acts upon these bodies, 
forming a precipitate which carries with it any suspended 
impurities of the wine. The great amount of tannin in the 
red wines permits the use of albumen, while isinglass is 
used with white wines. 

Acid potassium tartrate is present in considerable quan- 
tity in the grape juice. The solubility of this salt decreases 



424 APPLICATIONS OF CHEMISTRY. 

with the increase of alcohol, so that the slight fermentation 
which goes on after the bottling or casking causes a depo- 
sition of the salt. With the removal of the tartrate the 
coloring matter becomes less soluble and falls, giving the 
wine a lighter color. 

In effervescent wines the fermentation is continued after 
bottling, and the carbon dioxide liberated under pressure 
is retained in the liquid. Champagne is the most im- 
portant effervescing wine. Its manufacture requires great 
care and skill, hence the wine is very expensive. For 
champagne the must or grape juice is very carefully clari- 
fied and the wine bottled before the fermentation has 
ceased, sugar being added at the same time, as there is not 
enough left in the wine to continue the fermentation to the 
desired point. After fermentation has taken place for a 
time in the bottles the corks are removed and the com- 
pressed gas discharges the yeast and other impurities. The 
bottles are then refilled with a specially prepared white 
wine or liqueur, recorked, and sealed for the market. The 
different processes require six or seven months, and during 
the fermentation in the bottles there is much loss due to 
breakage. In the dryest champagnes the pressure of the 
gas often reaches five or six atmospheres. 

In the manufacture of red wines it was formerly the 
custom in wine-making countries, and still is in some 
places, to crush the grapes by the bare feet of men tread- 
ing upon them. This crushing is the preliminary to the 
pressing of the grapes. In the making of champagne the 
grapes are not crushed before being put into the presses, 
the only crushing being by the press ; this gives a purer 
juice. 

The reason that the grape is superior to all other fruits 
for wine-making is that its vegetable salt is potassium 
tartrate, which, as above explained, is deposited as the 
alcohol increases and the sugar disappears. Wine made 



ALCOHOLIC BEVERAGES. 425 

from gooseberries, currants, apples, etc., contains malic 
and citric acids, which cannot be thns removed, and con- 
sequently their acidity must be overcome by the addition 
of sugar. 

Cider is a wine which results from the fermentation of 
the fruit sugar of the apple. It may contain from seven to 
ten per cent of alcohol. 

A solution containing more than one third its weight of 
sugar will not undergo vinous fermentation, and when the 
alcohol produced amounts to about seventeen per cent of 
the solution the fermentation ceases. This limit fixes the 
maximum strength of fermented liquors. 

DISTILLED LIQUORS. 

The stronger alcoholic beverages of mankind result from 
the distillation of fermented liquors. They may be 
brought into two general classes, whiskies and brandies. 

Brandies. These result from the distillation of wines. 
The brandy from grape- wines is considered the best. In 
this country a brandy is made from apple cider and one 
from the juice of the peach. 

Whiskey. Whiskey is made by distilling the fermented 
products of various starchy substances. Those generally 
used are Indian corn (maize), rye, barley, rice, and oats. 
In the United States whiskey is made in large quantity, 
corn and rye being the principal grains employed. That 
from corn is, in this country, generally known as Bourbon 
whiskey. 

The grain is malted quite similarly as for beer, but as 
the diastase for the malt is far greater than necessary to 
convert its starch into sugar, distillers generally add a large 
portion of unmalted grain whose starch is also converted. 
The extract from the grain is fermented as in beer-making, 
and as the distiller endeavors to produce as much alcohol 
as possible the fermentation is urged to its utmost. This 



426 APPLICATIONS OF CHEMISTRY. 

fermented liquor is then subjected to distillation, the por- 
tion passing over during the process constituting the 
whiskey, the residuary liquid being of little value. The 
alcoholic strengths of both fermented and distilled liquors 
vary between wide limits, and there is such a large number 
of each kind that it is impracticable to here give special 
definitions. The genuine wines, whiskies, and brandies 
are, to a considerable extent, now imitated by mixing 
liquors of different strengths and adding certain flavoring 
and coloring materials. 

BREAD-MAKING. 

The essential constituents of bread-making grains are 
water, starch, nitrogenous matter, dextrin, cellulose, a little 
sugar and some fat, and inorganic salts. The nitrogenous 
matter is mainly in the form of gluten and albumin. The 
gluten is composed of vegetable fibrin, of a substance re- 
sembling casein, and of vegetable glutin. The gluten is the 
most important constituent for bread-making. It is be- 
cause of the tenacity of the wheat gluten that it is superior 
to all other grains for bread-making. This tenacity is due 
to the vegetable glutin or gliadin ; it is this component of 
the gluten that gives adhesiveness to the dough. 

When wheaten flour is kneaded upon cloth the gluten is 
left as an elastic, tenacious mass. The gluten is the main 
flesh-forming constituent of the flour, but in its natural 
state it is tough and difficult of digestion. In good bread 
the dough is so manipulated that the whole is rendered light 
and porous, thus becoming more palatable and more digesti- 
ble, exposing a large surface to the action of the digestive 
fluids. Rye stands next to wheat as a bread-making grain, 
and it is largely used for that purpose in northern Europe. 
Wheat is the chief bread-making grain. 

The essential and desired qualities of lightness and 
porosity are conferred upon bread by incorporating with the 



BREAD-MAKING. 427 

dough carbon dioxide under pressure. The tenacity of the 
gluten prevents the ready escape of the gas, and by its 
expansion the required texture is produced in the dough. 
This vesiculated texture is made permanent in the bread by 
the solidification which results from baking. 

The carbon dioxide employed may be produced by fer- 
mentation within the dough, or otherwise introduced therein. 
In the former case fermented bread results, in the latter 
unfermented. 

Fermented Bread. In this kind of bread various kinds of 
yeast are employed, the result being a vinous fermentation, 
by which the sugar of the dough is converted into carbon 
dioxide and alcohol. These escaping through the gluten 
cause the dough to rise. A little yeast incorporated with 
some dough is placed in a suitable temperature. When this 
charge has worked awhile, it is kneaded with the remaining 
batch of dough. The fermentation then pervades the whole, 
and after a short interval the loaves are formed and placed 
in the oven. 

Sometimes leaven is employed to bring about fermenta- 
tion. Leavening has been practised from remote ages. It 
consists in placing a small quantity of dough under favor- 
able conditions to undergo natural fermentation, and when 
this has set in, the leaven is mixed with the dough and the 
whole undergoes fermentation. In this case the cause of 
the fermentation is minute organisms introduced into the 
dough from the air. 

In fermented bread the sugar, which is fermented, is that 
present in the grain, and it is also partly derived from the 
conversion of starch into sugar. It is seen that vinous fer- 
mentation x>lays an important part in bread- making. A 
considerable amount of alcohol is given off in the making of 
such bread, and it acts like the carbon dioxide to lighten 
the bread. Efforts have been made to collect and save the 
alcohol given off in the manufacture of fermented bread, 



428 APPLICATIONS OF CHEMISTRY. 

but the necessary arrangements for this purpose injured 
the quality of the bread and were abandoned. 

Unfermented Bread. The most direct method of preparing 
unfermented bread is illustrated in the making of aerated 
bread. In this process the flour is brought to the state of 
dough by kneading with water charged with carbon dioxide. 
The whole operation is mechanically performed in closed 
vessels. When the mixing is complete an opening is made 
at the lower part of the vessel and the dough is forced out 
by the pressure of the gas. The vesiculation is produced 
by the expansion of the gas, with which the dough is 
thoroughly impregnated. The expansion begins when the 
dough is removed from the vessel, and is still further in- 
creased by the heat of the oven. In this process the dough 
and bread are untouched by the hands of the baker until 
removed from the oven. 

Unfermented bread is also made by the use of certain 
powders, which react upon each other when moistened with 
water and liberate carbon dioxide. The most common of 
these is a mixture of tartaric acid and acid sodium car- 
bonate. If the powders be thoroughly incorporated with 
the flour, the gas will be liberated during the kneading with 
water. Another method is to mix the sodium carbonate 
with the flour and then knead with slightly acidulated 
water ; dilute hydrochloric acid is frequently employed. 
Ammonium carbonate alone is sometimes used, it being 
volatile at the temperature of baking. 

Flour is injured if it becomes damp or moist, its gluten, 
becoming somewhat soluble and less tenaceous. Such flour 
is greatly improved by adding to the water used in making 
the dough, lime water in the proportion of twenty-seven 
pints to one hundred pounds of flour. 

Hard Bread. This kind of bread is made by baking the 
prepared dough without vesiculating material of any sort. 
All the moisture is expelled from such bread and it is much 



SOAP-MAKWG. 429 

i 

more dense than soft bread and keeps far better. It is 

accordingly better for military and naval stores. Other 

grains than wheat and rye can be used for making hard 

bread. 

One hundred pounds of flour will make considerably 
over one hundred pounds of soft bread, depending urjon the 
proportions of the crust, and this depends upon the size of 
the loaves. Ordinarily the weight of soft bread will exceed 
the weight of flour by about one third. The weight of hard 
bread is less by about one seventh. The staleness of bread 
is not due to its becoming dry, as is frequently supposed, 
but results from molecular change. Its freshness can be 
restored by rebaking in a closed oven. 

The cereal grains are richer in inorganic salts and fatty 
matter in and near the husk. As there is frequently some 
of the integument carried away with the husk, it is evident 
that unbolted flour has some superiority over the bolted. If 
bread supplied the only article of food, this difference be- 
tween the flours would be more important. Besides the 
physical condition of bread which makes it more palatable 
and more digestible than dough, other important changes 
are brought about by the baking. The state of the nitro- 
genous constituents is altered and made more digestible. 
The granules of starch are ruptured and some of it trans- 
formed into dextrin and sugar, both of which are soluble ; 
this latter effect is especially noticeable in the crust and in 
toasted bread. 

THE PREPARATION OF SOAP. 

A fuller account of the fats and fixed oils than has yet 
been given will lead to a better understanding of the 
chemical principles of soap-making. 

Fixed Oils ; Fats ; Glycerides. These are terms applied to 
a large number of analogous bodies found in both plants 
and animals. It is an interesting fact that there should be 



430 APPLICATIONS OF CHEMISTRY. 

such a striking resemblance in composition and properties 
between bodies from such distinct sources. 

The term fixed oils is generally used for those members 
of the group which are liquid at ordinary temperature, and 
the term fats for those that are solid. A fat is a so] id 
fixed oil. 

These bodies are ethereal salts of the fatty acids. The 
basic part of the salt is the alcohol radical C 3 H B . They are 
all capable of saponification, yielding glycerine and a fatty 
acid. Owing to the above facts the class is very properly 
termed glycerides. Some of the characteristics of the 
glycerides are as follows. 

Composition. They are all composed of carbon, hydro- 
gen, and oxygen, being very rich in hydrogen and carbon. 
They yield glycerine and a fatty acid by saponification. 

Solubility. They are practically insoluble in water, 
but dissolve in ether and carbon disulphide, and mix in all 
proportions with essential oils. 

Stability. If the air be excluded they can be preserved 
for a long time. In contact with air some of them absorb 
oxygen, and in thin layers become solid. Such of the fixed 
oils are called drying oils. This oxidation may take place 
with considerable elevation of temperature. If the oil ex- 
poses a large surface, as when tow or cotton waste is moist- 
ened with it, spontaneous combustion may result. Other 
of the fixed oils when exposed to the air do not dry up, but 
become rancid and ropy. This change is attributed to the 
presence of impurities. Such oils are called non-drying. 
The fixed oils cannot be distilled without decomposition. 
They are unctuous to the touch, and the more liquid leave 
a permanent stain on paper. 

Some of the more important of these oils and fats are 
the following : palm, cocoa-nut, castor, cotton-seed, and 
olive or sweet oil. Hemp, poppy and linseed oil are drying 
oils, the last named being much used by painters. Its 



SOAP-MAKING. 431 

drying powers are increased when it is boiled with cer- 
tain metallic oxides. Such oxides are termed siccatives. 
The oils just named are of vegetable origin. Some of the 
other common ones obtained from animal sources are 
stearin, palmitin, margarin, and olein. Butter is mainly 
composed of palmitin, stearin, and olein. Beeswax is a 
fat. 

It will be seen that the above characters establish a 
broad distinction between the fixed oils and the essential 
or volatile oils. 

MANUFACTURE OF SOAP. 

Soap manufacture is an ancient and important industry. 
The remains of a complete soap-making establishment were 
found in the excavations of Pompeii, with soap still per- 
fect though made over seventeen hundred years ago. 

It has just been stated that the more important vege- 
table and animal fats and oils are composed of a fatty acid 
in which the hydrogen is replaced by C 3 H 5 , the radical of 
glycerine or propenyl alcohol, the oils and fats being 
glycerides. The general significance of the term saponifi- 
cation has been given. Soap is here used in the ordinary 
sense. 

The natural fats or glycerides may be represented by 
the formula C3H 5 Ft 3 , in which (Ft) stands for a complex 
molecule of carbon, hydrogen, and oxygen. The fatty acid 
from which the glyceride is derived would be represented 
by FtH. A soap may be defined as the salt of a fatty acid 
in which the hydrogen has been replaced by an alkali 
metal. 

Soaps are made by the action of an alkali upon the 
glycerides (fats), or sometimes upon fatty acids. The alka- 
lies employed are potassa and soda. The action is brought 
about by boiling the fat with the caustic solution, and may 
be indicated by the equation 



432 APPLICATIONS OF CHEMISTRY. 

C 3 H 5 (Ft) 3 + SKaOH = 3NaFt + C 3 H 8 3 . 

Soda Soap Glj*cerine 

Potassium hydroxide may be used instead of sodium hy- 
droxide, with the resulting production of a potash soap. It 
will be observed that the alkali metal has replaced the 
basic radical C 3 H 5 . Soaps are generally stearates, oleates, 
or palmitates of potassium and sodium. 

Soaps containing sodium are generally hard, and those 
containing potassium are generally soft, though it is possi- 
ble to produce a soft soda soap and a hard potassium soap. 
The soaps of the alkali metals are soluble, those of other 
metals generally insoluble. 

Soap can be produced from a large number of fats and 
oils, but only a comparatively small number is employed. 
The principal animal fats are tallow, suet, lard, whale, seal, 
and fish oils ; the vegetable oils commonly used are palm, 
olive, cocoa-nut, and cotton-seed. Fish oils contain a large 
proportion of olein, a liquid fat, and are generally used 
with potash to form soft soap, especially in Europe. In 
this country the farmers in the South and Southwest fre- 
quently make soap for domestic use from kitchen fats and 
the alkali obtained from wood-ashes. 

The alkali used is generally in the form of the hydroxide 
when soaps are made from fats. Certain soaps are made by 
boiling the alkaline carbonates with free fatty acids obtained 
in other operations. The alkaline hydroxides are prepared 
in enormous quantity for use in soap-making. 

The glycerine formed during saponification may or may 
not be separated from the soap. Castile soap is made from 
olive oil, and marine soap from palm oil. The subsequent 
treatment of the soap, after removal from the boiling ves- 
sels, depends upon the object desired and is very varied. 
Many different kinds of ingredients are incorporated for 
the purpose of affecting the color, odor, and other proper- 
ties of the soap. Soap may contain from 25 to 75 per cent 



LEATHER. 433 

of water. In the high dry regions of our Western country 
soaps have been known to lose nearly one half their weight 
by evaporation of the water contained. 

Cleansing Power of Soap. This property of soap is largely 
due to its alkalinity. Even a neutral soap gives an alkaline 
solution when treated with water, some of the alkali sepa- 
rating and leaving a soap with a greater amount of fatty 
acid than previously existed. The excess of a] kali acts 
upon the grease or other insoluble matter, and often renders 
its removal possible. To increase the detergent power of 
soap, substances are sometimes added which act merely 
mechanically; such are sand and silicate of sodium. 

MANUFACTURE OF LEATHER. 

The antiquity of this industry is unknown, but it is cer- 
tain that it was practised by the ancient Egyptians, for 
pieces of leather taken from a mummy, and now in the 
British Museum, bear marks showing that it must have 
been made 900 years B.C. It is well known that the Ro- 
mans attained much skill in the preparation and finis hing of 
leather, and it is thought that the Chinese were acquainted 
with the art from remote ages. On the other hand it is 
strange, when we recall how universally the skins of ani- 
mals are used by savages, that so many of them should have 
remained ignorant of the art of tanning almost up to the 
present time. 

Leather. If the fresh skin of an animal, cleaned and 
divested of hair, fat, and other extraneous matter, be im- 
mersed in a dilute, solution of tannic acid, a chemical com- 
bination ensues ; the gelatinous tissue of the skin is con- 
verted into a non-putrescible substance, impervious to and 
insoluble in water ; this is leather. 

TANNING. 

Preparation of Hides; Cleansing. The first step in the 
preparation of leather is the softening and cleaning of the 



431 APPLICATIONS OF CHEMISTRY. 

\ les. This is done by soaking in water, with frequent 
changes, until the skins are pliable. They are then put 
through a kneading process. The length of time that the 
hides must be soaked depends upon the manner of their 
original curing. The hides from hot dry countries some- 
times require two or three weeks' soaking. 

Depilation. The hair is removed from the cleaned skins 
by soaking them in lime water ; the lime saponifies the fat 
around the roots of the hairs and loosens them : or the same 
result may be accomplished by what is termed sweating. In 
this process the hides are suspended in pits and kept at a 
uniform temperature (18° C.) and in a moist atmosphere 
until they undergo partial decomposition. The ammonia 
produced acts in the same way as the lime. The sweating 
process is almost exclusively followed in this country in the 
treatment of dried hides. The time necessary in this opera- 
tion varies with the character of the hides treated, so that 
no particular statement applies. 

After the hair is scraped off, the hides are treated for the 
removal of lime, when this substance has been used as a 
depilatory. This is usually accomplished by steeping in a 
dilute solution of sulphuric acid. In this country hides for 
heavy leather are generally subjected to acid treatment, 
though the sweating process has been employed. The acid, 
if properly used, exerts a beneficial action in preparing the 
skin for tanning. The acid is said to plump the fibre. In 
leathers which are required to be soft it is found necessary 
to remove the lime by treating the hide with some putre- 
factive or fermenting bate. This softens the hide by its 
action on the fibrous tissue and abates plumpness. Such 
bates are sour bran, hen's or pigeon's dung. 

Conversion into Leather. In this country the tanning 
materials used are almost exclusively oak and hemlock 
barks. The greater part is tanned by hemlock. The bark 
is first thoroughly ground and then leached to extract the 



LEATHER. 435 

tanning principle from it. The bark liquors are run into 
the vats, where the hides are packed. The hides are suc- 
cessively transferred to vats in which the liquor is stronger. 
In many American tanneries the process is completed in 
from sixty to seventy-five days from the time the hides are 
first subjected to the action of the liquors. 

In England and America the tanning materials are gen- 
erally leached or exhausted, and the aqueous extract or 
decoction used in the tanning vats. The operation of tan- 
ning is thus shortened. 

On the continent of Europe, and at many places in this 
country, after the hides are subjected to a weak infusion of 
the bark, they are packed in pits with alternate layers of 
bark ; the pit is filled wi th water and the whole left for two 
or three months. The hides are then removed and treated 
in the same way in another pit with fresh bark, the order 
of the hides in the pit being reversed at each transfer. By 
this method the tanning often requires from ten to fifteen 
months. During tanning the hide increases in weight 
from 30 to 40 per cent. 

The above description applies to the common heavier 
leathers. Many different tanning materials are used in 
different countries and a great variety of leathers produced ; 
of these it is here practicable to refer to only a few of the 
more common forms. 

Morocco. The genuine original morocco was made from 
goat-skins, but it is now said that an equally good article 
is made from the skin of the hairy seal. Imitation morocco 
is made from sheep-skins. With morocco the depilation is 
by lime, and the lime is removed by bate (pigeon' s dung). 
The skins are tanned by extract of sumach. They are sewed 
into bags, filled with the tanning liquid and floated in a tank 
of the same. The process is usually complete in twenty- 
four hours. Morocco is generally colored after the tanning, 
and the aniline dyes are largely used for this purpose. 



, 



436 APPLICATIONS OF CHEMISTRY. 

Russian Leather. This form of leather is tanned with 
willow or larch bark. It owes its peculiar odor to the 
essential oil of birch-tar, with which it is treated after 
tanning. Many imitations of this leather are now made. 

Tawing. Kid. The leather for kid gloves is made from 
the skin of goats and lambs. The skins are deprived of 
hair by lime, and the lime removed by sour bran. The tan- 
ning is accomplished by agitating the skins in a drum 
contaiuing a mixture of flour, alum, salt, and yolk of eggs. 
The aluminum chloride produced prevents putrefaction of 
the skin ; tlie oil and albuminous matters increase softness 
and pliability. This process is called tawing. The kid is 
colored after tawing. 

Buckskin ; Chamois Leather. These leathers are made from 
the skins of goats, sheep, and deer. The skins are prepared, 
limed, and bated in the same manner as for morocco. They 
are then thoroughly impregnated with fish, whale, or other 
oils by repeated steeping and drying. All the water of 
the hides is thus removed and its place taken by oil. The 
skins are then exposed to a warm atmosphere ; during the 
exposure some of the oil oxidizes and the skins take a 
yellow color. The excess of oil is then removed by an 
alkaline solution. It is not thought that any chemical 
change occurs in the skin itself, but the fibres are coated 
by the oily products and are very permanent and will not 
yield gelatine with boiling water. Kid does yield gelatine. 
Thicker hides than those above named may be used for this 
leather, but in that case they are made thin by splitting 
and rejecting the grain side. 

Animal Parchment. This parchment is made by the 
mechanical treatment of lamb and goat or other thin skins 
after the hair is removed in the usual way. The skins are 
stretched on frames and reduced to the necessary thickness 
by rubbing with sand or pumice-stone. 

It is now possible to imitate very closely the natural 



CHEESE. 437 

grain of any leather. The thickness desired can also be 
secured, for the modern splitting machines have succeeded 
in splitting a common cow-hide into three and even four 
layers. By these means all the fancy kinds of leather can 
be imitated. Split leather is not so lasting as the natural 
skin of the same thickness, but it is cheaper. The splitting 
is best done before tanning. The skins from which leathers 
are made are those of the ox, horse, sheep, goat, pig, seal, 
deer, and kangaroo. 

PREPARATION OF CHEESE. 

For the better understanding of the process of cheese- making it will be 
well to specify the composition of milk. The milk of all animals, both 
carnivorous and herbivorous, contains about the same constituents, though 
the proportions of the constituents vary considerably. 

Milk consists essentially of water slightly alkaline, in which are dis- 
solved casein, milk sugar, and inorganic salts, and in which float numerous 
fatty globules. The fatty matter is the source of butter. 

Good fresh milk is alkaline. Its alkalinity is due to soda, which holds 
the casein in solution. If left to itself it soon becomes acid, from the for- 
mation of lactic acid through the fermentation of the milk sugar. Milk is 
admirably adapted to the nourishment of the animal frame. 

Cheese-making. — Cheese is made by coagulating the milk by the addi- 
tion of rennet, which is part of the stomach of the calf. A piece of rennet 
is added to a large quantity of milk, which is then slowly heated to about 
50° C. In a short time after this temperature is reached the milk separates 
into a white coagulum or curd, and a slightly yellow translucent liquid 
called whey. The curd contains the casein of the milk, much of the fat, 
and some of the inorganic salts. The whey contains the sugar, some of the 
fat, and the remainder of the inorganic salts. 

The curd is separated from the whey, well kneaded with some common 
salt, and often some coloring substance is added. It is then pressed in 
moulds and set away in an airy and cool place to ripen. During the ripen- 
ing the cheese undergoes a peculiar putrefactive fermentation, not well 
understood, by which it acquires its characteristic taste and odor. The 
changes during ripening are brought about by the decomposition of the 
casein, and probably of some of the fat. 

The quality of the cheese, of course, depends upon the kind of milk em- 
ployed and the extent to which the ripening is carried. The amount of 



438 APPLICATIONS OF - CHEMISTRY. 

fat largely determines the quality of the cheese, the best qualities contain- 
ing considerable fat, while the poorer are made from skimmed milk. The 
vesicular appearance of certain kinds of cheese is caused by the imperfect 
removal of the whey from the curd. The sugar of the whey ferments dur- 
ing the ripening, producing alcohol and carbon dioxide ; these expanding 
produce the vesicles. Cheese with less fatty matter keeps better than 
richer cheese. 

From the constituents of cheese it is evident that it possesses consider- 
able dietetic value. In many places it is an important article of daily diet. 
Cheese can be made from the milk of any animal, but generally comes 
from the milk of the cow; it is a product of many countries. It is very 
largely made in this country and of excellent quality. The curd can be 
separated by adding a little acid to the milk and heating, but this is seldom 
done in cheese-making. 

The successful preparation of artificial butter (oleomargarine) has led, 
in some places, to the use of this substance for the fatty principle of cheese, 
thereby permitting the use of skimmed milk. It is reported that this is 
sometimes done in our country, and that cotton-seed oil is also used for 
the same purpose. 

The red and blue moulds which grow upon cheese are vegetable fungi. 
The cheese maggot and the cheese mite are animal organisms. Cheese, like 
meat, may and has been known to undergo decomposition with the devel- 
opment of poisonous properties. 



DYEING. 

Dyeing is the art of imparting color to various substances, usually 
textile fabrics, in such manner that it is permanent under the conditions to 
which the fabric is subjected. In dyeing, the color penetrates the material 
dyed, which is not the case in painting. 

In order that the dye may penetrate the fabric it is evident that the 
former must be in solution. It is often only necessary to steep the fabric 
in a solution ei the coloring matter, the attraction between the two im- 
parting a permanent color. In the absence of the necessary attraction be- 
tween the fabric and the dyestuff, a third substance is employed which 
:h as an attraction for both; such substances are called mordants. When 
mordants are used there are usually two steps in the operation of dyeing: 
:first, the application of the mordant; second, of the coloring matter. The 
nature of the action between the fabric and the mordant, and between the 
fabric and the dye when mordants are not used, is not clearly understood. 



DYEING. 439 

The facts and evidence at present seem to indicate that in some cases the 
action is physical, and that in others it is chemical. 

In cotton, linen, and vegetable substances generally, the action seems 
to be more of a physical one than in the case of silk, wool, and other 
animal substances. As a general fact the coloring material permeates the 
latter class more fully than the former, and they may be dyed with greater 
facility and more permanently; the vegetable substances more frequently 
require mordants. The action between the mordant and the dye is in most 
cases a chemical one. 

Mordants. The mordants can generally be classed as acid or basic. 
The principal mordant of the first class is tannic acid. Other vegetable 
acid principles and some fatty acids are used for the same purpose. The 
basic mordants comprise a number of metallic salts, the principal of which 
are salts of aluminum, iron, chromium, and tin. 

The processes of mordanting cloth are too numerous even for present 
mention. The fibers of the cloth are impregnated with the mordanting 
substances in soluble form, and by subsequent treatment it is rendered in- 
soluble, if not naturally so after its union with the fiber. Usually mor- 
danting precedes dyeing, but sometimes the operations are simultaneous, 
and occasionally the dyeing precedes the mordanting. 

Dyestuffs. The chemical character of many of the numerous dyestuffs 
classes them as either basic or acid. Each of them requires to be combined 
with a mordant of the opposite character to yield a dye. 

We may illustrate the mordanting action by a simple case. If cotton 
be steeped in a solution of tannic acid it will absorb it; if it is then dipped 
into a solution of a basic coloring matter the acid combines with it and 
the fiber is dyed. Again, if cotton be steeped in a solution of aluminum 
acetate and then boiled, a basic acetate is deposited in the fiber. If the 
cotton be now dipped into the solution of an acid coloring principle it will 
be permanently dyed. 

Cloth-printing. If the dye be applied to only parts of the cloth, so as 
to produce patterns, it is called printing. In goods requiring mordants, 
this is easily accomplished by mordanting only those parts to be printed. 
Sometimes the cloth is uniformly dyed and the pattern effect produced by 
removing the color from certain parts. This can be done by bleaching 
agents and is known as the discharge method. 



INDEX. 



PAGE 

Acetates 365 

Acetic ether 366 

Acetone , 366 

Acetylene 103 

preparation of 104 

series 348 

Acid, acetic 362 

preparation and properties of 362 

glacial 363 

arsenic 168 

arsenious 167 

citric 367 

gallotannic 368 

hydrobromic 137 

hydrocyanic 370 

hydrofluoric 139 

hyposulphurous 158 

malic 367 

metaphosphoric 165 

nitro-muriatic 135 

orthophosphoric 165 

oxalic 366 

pyrophosphoric 165 

pyrosulphuric 157 

sulphydric, hydrosulphuric 144 

sulphuric 150 

sulphurous 150 

tannic 368 

tartaric 367 

thiosulphuric 158 

Acids 23 

basicity of 25 

neutralization of 19S 

strength of 177 

441 



442 INDEX. 

PAGE 

Affinity, force 2, 172 

and valency contrasted ; 52 

Affinities, relative 172 

African gold mines 337 

Aqua Regia 135 

Air, atmospheric 71 

Albumin, egg 382 

plant 3S2 

serum 382 

Albuminoids 381 

Albumins 381 

Alcohol, common ethyl 356 

preparation of 358 

methyl 356 

propyl 359 

Alcoholic beverages 420 

Alcohols, monohydric 356 

trihydric 359 

primary 361 

secondary and tertian,- 362 

Alkali metals .200 

Alkaloids 384 

Alloys 55 

Alum, ammonium 258 

common 257 

Alumina 259 

Aluminum occurrence, preparation 255 

properties, uses 256 

hydroxide 259 

sulphate 257 

Ammonia 119 

chemical properties 121 

physical properties 120 

preparation 122 

Ammoniacal liquor 415 

Ammonium 237 

chloride and sulphate , 238 

carbonate, acid 239 

nitrate 239 

sulphide 240 

Amyloses 376 

Anhydride, acid 24 

basic 23 

Anion 191 

Antimony 291 



INDEX. 443 

PAGE 

Argon 169 

Aromatic hydrocarbons 349 

Arrow-root 350 

Arsenic, preparation, properties 166 

oxides and sulphides of 168 

trihydride 168 

Artiads 49 

Atmosphere, unit of pressure 62 

Atmospheric air 61 

carbon dioxide in 63 

composition of 62 

minor components 64 

physical properties 62 

solid constituents of 64 

Atomic theory 6 

weights 28 

table of 3 

by analysis 29 

from Avogadro's law 36 

by decomposition 31 

from isomorphous relations 42 

specific heat 45 

by substitution 30 

Atoms, definition 8 

number in molecules 39 

Avidity defined 178 

Avogadro law of 32 

use in determining atomic weights 36 

Balsams 323, 351 

Barium and carbonate of 240, 241 

chlorate 246 

chloride 242 

hydroxide 242 

nitrate 241 

sulphide 242 

sulphate 241 

Base 21 

Bases, strength of 177 

Basic anhydride 23 

Beer-making 420 

Bellite 460 

Benzene series » 349 

Beryllium -.-, 255 

Bismuth 292 



444 INDEX. 

PAGE 

Borates 142, 119 

Borax 236 

Boric oxide and acid 118 

Boron 118 

Brandies 425 

Bread, fermented . , 427 

hard 428 

Bread, unfermented 428 

Bread-making 426 

Brewing 421 

Britannia metal . , 293 

Bromine, preparation, properties 136 

oxyacids of 137 

Brush, C. F 74 

Buckskin 436 

Bunsen burner Ill 

Cadmium , 254 

Caffeine , 383 

Caesium 240 

Calcium 242 

carbonate 243 

chloride 247 

fluoride 247 

hydroxide 244 

oxide 243 

salts, reactions of 247 

sulphate 246 

anhydrous 245 

sulphide 247 

Calorific value or power 385 

intensity 386 

Camphors 351 

Cane sugar 374 

preparation and properties 375 

Carbohydrates 372 

Carbolic acid 371 

Carbon 87 

amorphous 94 

compounds, classification of 340 

dioxide 95 

effects on system 97 

chemical and physical properties of 96, 97 

preparation of 99 

disulphide, preparation, properties and uses 158, 159 



INDEX. 445 

PAGE 

Carbon, mono- and trisulphide 160 

monoxide, properties and uses 100 

Carbonic acid and its salts 99 

Carborundum 118 

Carmine 380 

Carre freezing apparatus 121 

Case-hardening 284 

Casein 382 

Caontchonc 350 

Catalysis 19 

Cathion 191 

Cavendish 65 

Celluloid 408 

Cellulose : 379 

Cerium 296 

Chamois leather 436 

Charcoal 112, 89 

preparation of 90 

properties and uses SiJ^f [ 

animal 82 

Cheese-making 437 

Chemistry, definition 2 

Chlorine 129 

preparation and properties 130 

uses 131 

compounds with silicon, boron, nitrogen . 135 

oxygen, compounds of 135 

Chromium 291 

important compounds of 291 

Cinnabar 327 

Cobalt 289 

chloride ' 289 

ultramarine 289 

useful compounds of 289 

Cocaine 384 

Coke 93 

Collodion cotton 407 

Combustion in general 60 

and flame 105 

flameless 115 

Composition to determine percentage 54 

Compounds, binary, nomenclature of 10 

Copper acetate 366 

carbonate 415 

extraction of silver and gold from '. . . . 312, 313 



446 INDEX. 

PAGE 

Copper, ores of, where found 307 

matte, bessemerizing of 310 

oxides 314 

properties of 313 

pyritic smelting without fuel 311 

reduction 307 

dry 308, 9, 10 

wet 311 

sulphates 314 

uses of 314 

Copperas 288 

Corpuscles 216 

Crasses 301 

Cryo-hydrates 77 

Cyanogen 370 

Dalton's atomic theory 7 

Dextrin 379 

Dextrose 373 

Diamond 87 

Diffusive power 66 

Disposing affinity 19 

Dissociation by heat 184 

by heat of steam 184 

by solution < . 185 

summary of theory 187 

Distilled liquors 424 

Dobreiner's lamp 329 

Dulong and Pettit, law of 45 

Dyeing, dyestuffs 438, 439 

Electrolysis 193 

Electrolytes and their osmotic pressure . 194 

Electrolytic Association 192 

Electrons . . 216 

Elements, classification of 2 

definition 7 

general 1 

number of 2 

state of aggregation 3 

table of 4 

weights, equivalent 27 

Emery 259 

Empirical and molecular formulae 55 

Endothermic and exothermic action 48, 128, 151 



INDEX. 447 

PAGE 

Equilibrium hetrogeneous 176 

homogeneous 176 

Ether, common, ethyl 368 

properties of 369 

Etherion 64 

Ethers, alcohol 368 

Ethine, acetylene, preparation of 103, 104 

Ethylene, olefiant gas 104 

Equivalent weights 27 

Explosive compounds 402 

mixtures 399 

Explosives, classes of ". 398 

defined 397 

Fats 429 

Fermentation, ferments 357 

Ferro-manganese , 291 

Fibrin 382 

Fire-ware 396 

Flame 106 

Flame, blowpipe 112 

candle . . , 109 

lighting 110 

luminosity of 106 

oxyhydrogen 116 

smokeless Ill 

structure of 107 

Flames, hydrocarbon 108 

Fluorine preparation, properties „ 139 

uses 140 

Formulae, constitutional 342 

structural 342 

rational 342 

Fruit sugar 344 

Fulminates 412 

Fusible metal 292 

Gas, coal, illuminating 413 

manufacture of 414 

secondary products from 418 

Gas, water 419 

Gallium 260 

Gelatine 381 

explosives 407 

dynamite 408 



448 INDEX. 

PAGE 

Germanium 296 

Glass, devitrified 392 

kinds of 390 

soluble 392 

Glass-making 388, 391 

Glucoses 373 

Glue 38 1 

Gluten 382 

Glutin 381 

Glycerides 429 

Glycerine 359 

preparation of 360 

properties of 361 

Glycerols 359 

Gold, amalgamating for 333 

chlorine leaching for 334 

cyanide leaching for 335 

compounds of 338 

from Africa . 337 

deposits, sedimentary 336 

quartz veins 333 

Gold, metallurgy of 332 

occurrence 331 

properties of 338 

Graphite 88 

Green vitriol 288 

Gums 379 

Gun-cotton 405 

Gunpowder, black, preparation of .' 401 

products from explosion of .' 399, 401 

Gutta-percha 355 

Gypsum 236 

Halogens 129 

Heat, dissociation by 184 

Heat of combustion 384, 388 

Heat of neutralization 200 

Helium 169 

Helium from radium 215 

Homologous series 345 

Hydracids 14 

Hydrazine , 123 

Hydrocarbons, aromatic 349 

characteristics of 344 

denned 341 



INDEX. 449 

PAGE 

Hydrocarbons, saturated 344 

unsaturated 347 

terpene 349 

Hydrochloric acid, preparation of 132 

action on metallic oxides 134 

properties 133 

Hydrogen 65 

chemical properties 67 

heat of combustion 68 

peroxide 86, 109 

physical properties 65 

preparation 69 

reducing action of 68 

Hyposulphurous acid 158 

India rubber 351 

vulcanized 353 

tubing and threads 354 

Indigo 380 

Indium 260 

Indurite 412 

Iodine, compounds of 139 

preparation, properties 137 

uses of 138 

Ionic conduction of electricity 200 

Ionic theory 188 

acids and bases under 197 

Ionogens 188 

Ions, importance in analysis 197 

independence of 195 

nature of 216 

notation and nomenclature of 194 

relation to rays 217 

Ionization, result of 193 

Iridium 331 

Iron, carbonate 287 

chemical properties of 286 

cast, composition and properties of 269 

furnace for reduction 266 

gases from 268 

metallurgy of 261 

occurrence 260 

ores of 261 

salts, reactions of 289 

sesquioxide 2S7 



450 INDEX. 

PAGE 

Iron, slag from furnace, uses of 266, 267 

sulphate, ferrous sulphate 288 

tetroxide 287 

wrought, from ores, Eames' process 275 

manufacture of 272 

mechanical puddling 274 

properties of 276 

puddling furnace 273 

Isomerism, isomers 343 

Isomorphism 42 

Kid 446 

Krypton 169 

Lac 380 

Lsevulose 374 

Lamp, safety 113 

Lampblack 89 

Laughing-gas 128 

Lavoisier 59, 65 

Law of Avogadro '. 32 

conservation of matter 3 

definite proportions 3 

even numbers 50 

insolubility 17, 175 

maximum work 73 

multiples 6 

volumes 43 

apparent exceptions to 44 

Lead acetate 365 

carbonate 404 

manufacture of 405, 406 

properties and uses 303 

desilverizing of 300, 301 

metallurgy of 297, 298 

Lead, oxides of 304 

properties and uses of 302, 303 

salts, reactions of 307 

Leather, manufacture of 433 

Russian 436 

Leblanc process 333 

Legumen, vegetable casein 382 

Lime 243, 244 

Lithium 240 

Litmus 380 

Liquors, distilled 425 



INDEX. 451 

PAGE 

Madder 380 

Magnesia 248 

Magnesium, compounds of 249 

preparation of, uses . 248 

sulphate 249 

Maltose 376 

Manganese 280 

oxides of 290 

Marsh-gas 102 

properties 103 

Mass, influence of in reactions 174 

law of action 174 

Matter, states of 170 

kinetic molecular theory of 171 

Maximum work, law of 204 

Mercuric cyanide 371 

Mercury, chloride of 327, 328 

metallurgy of 324 

occurrence 323 

oxides of 328 

properties of « 325 

sulphide . . . . 327 

uses of 326 

Metalepsis 135 

Metamers 343 

Metargon 169 

Methane : 121 

Methyl alcohol 356 

Microcrith 34 

Minium 304 

Mixtures 4 

Molecule, definition of 7 

saturated, unsaturated 50 

Molecular and empirical formulae 55 

weights, determination of 35 

Molecular weights, from Avogadro's law 32 

depression of freezing-point 36 

lowering of vapor pressure 36 

osmotic pressure 35 

Molybdenum 292 

Monium 169 

Mordants 260, 365, -439 

Morocco 435 

Morphine 383 

Myosin . 3S2 



452 INDEX. 

PAGE 

Nascent state 18 

Neon 169 

Nickel 290 

Nicotine .."..< 383 

Niobium 293 

Nitrates 127 

Nitre * 125 

Nitric acid, preparation, properties, uses 124, 127 

oxide 128 

Nitro-compounds 408 

of benzene 409 

and organic nitrates 410 

Nitro-glycerine 403 

derivatives n 404 

properties 404 

Nitro-muriatic acid , 135 

Nitrogen 70 

chemical properties 70 

physical " 70 

as plant food 119 

preparation 71 

and oxygen, compounds of 123, 129 

Nitrous oxide 128 

Nomenclature 10 

Notation, chemical 8 

Oils, fixed 429 

Occlusion 67 

define series 348 

Opium 383 

Organic chemistry 339 

compounds, organized bodies 340 

Osmium 331 

Osmose 67 

Osmotic pressure 181 

Oxidation 62 

Oxides, metallic 23 

nomenclature of 10 

Oxy-acids 11 

Oxygen, action on metals 61 

non-metals 60 

chemical properties . 60 

discovery 59 

physical properties 59 

preparation of 62 



INDEX. ' 453 

PAGE 

Oxygen and nitrogen, compounds of 123 

Ozokerite 347 

Ozone 64 

chemical properties of 64 

detection of 65 

physical properties of 64 

preparation of 64 

Palladium 381 

Paraffins, general formula 342, 45 

Parchment, animal 436 

Parke's desilverizing process 301 

Pattinson's " " ' 301 

Periodic arrangements of elements 207 

Periodic law 207 

Perissads 345 

Petroleum, source of, products from 346 

Pettit and Dulong, law of 45 

Phenic acid '. . 371 

Phenol 371 

Phosphorous, amorphous, red 163 

hydrogen, compounds of 165 

occurrence, preparation 161 

oxides and oxy-acids of 165 

properties of 163 

uses 164 

Picric acid 409 

Plaster of Paris ; 246 

Platinum, black 330 

chloride , 331 

occurrence, preparation 328, 329 

properties of 329 

Polonium 169 

Polymerism, polymers 343 

Porcelain, decorating 385 

hard . , 385 

Sevres and Meissen 393, 394 

soft 395 

Potassium bicarbonate 225 

bromide „ 226 

Potassium carbonate, preparation 223, 224 

properties, uses 224 

chlorides 226 

chlorate 228 

chromates of 291 



454 INDEX. 

PAGB 

Potassium, cyanide 371 

ferricyanide 371 

ferrocyanide 370 

hydroxide 225 

iodide 226 

nitrate 226 

properties of 227 

occurrence 221 

oxides 229 

preparation 222 

properties, uses of 223 

sulphates 229 

Pottery 393 

kilns , 396 

Powder, smokeless 411 

Priestly 59, 64 

Printing, cloth 439 

Properties of common classes of salts 53 

Pyrites 288 

Pyrolusite 290 

Pyro-sulphuric acid 157 

Pyroxylin 405 

soluble 439 

Quantivalence 48 

classification according to 49 

Quinan, W. R 154 

Quinine 384 

Rack-a-rock 409 

Radicals 20 

electro-negative or positive 21 

Radioactive elements 212 

emanations from .-;. 215 

properties of . 216 

rays from 217 

Radioactivity, nature of 218 

Radium 169 

Radium salts, properties of 213 

heat from 215 

Reactions as affected by insolubility 17 

nascent state, physical surroundings 18 

pressure 19 

solution 17 

temperature 17 

volatility 18 



INDEX. 455 

PAGE 

Reactions, chemical 14 

classes of 15, 173 

complete phenomena of 206 

complete, reversible 175 

determining causes 16 

influence of mass 174 

Reducing agent — reduction 68, 91 

Resins 351 

Rhodium 331 

Rochelle salts 367 

Rubidium 240 

Ruthenium 331 

Rutherford 93, 70 

Saffron 380 

Sago 378 

Sal- volatile 239 

Salt, anhydrous 27 

basic 26 

primary or acid 25 

secondary 25 

Saltpetre 226 

Salts, how defined 26 

Selenium 160 

Siderite .„ 287 

Silica 117 

Silicon 116 

Silver chloride 323 

nitrate 322 

occurrence, smelting for 305 

ore, wet and dry stamping 319 

properties of 321 

pure, to manufacture 322 

reduction, by amalgamation 326 

at Comstock lode 318 

by Freiburg method 318 

leaching 320 

salts, reaction of 323 

uses of 322 

Slag, iron 266 

Smalt 2S9 

Smelling salts 239 

Smokeless powders 401 

Soap, manufacture of 401 



456 INDEX. 

PAGE 

Soap, cleansing power of 433 

Sodium 229 

acetate : 366 

biborate 236 

bicarbonate 235 

Sodium carbonate, preparation 233, 234 

properties, uses 235 

chloride, occurrence and preparation 231, 232 

hydroxide 235 

nitrate 235 

properties, uses 230 

silicate 237 

sulphate 237 

thiosulphate 237 

Solution, dissociation 187 

of gases and liquids 77, 78 

solids 76 

Solutions, electrolytic 190 

isotonic 182 

kinds of 178 

normal 179 

terminology employed 178 

theory of 179 

Solutions, electrolytic 190 

Specific heats and atomic weights 45 

Speiss , -. 299 

Spiegeleisen 291 

Springs, petrifying , 84 

Stamp mills 316 

Starch 376 

Steel, cementation 281 

crucible 283 

manufacture, Bessemer process 277 

open hearth process 279 

Siemens-Martin process . 281 

properties of 285 

shear 283 

Stochiometry 54 

problems of weight 56 

volumes 57 

Strychnine 384 

Sucrose 374 

Sugar of lead 365 

Sulphates 156 



INDEX. 457 

PAGE 

Sulphur, chemical properties 143 

compounds with hydrogen 144 

oxygen 148, 171 

Sulphur dihydride, hydrogen sulphide 144 

action upon metals and oxides ... 145 

action with salts 145 

occurrence, properties 144 

preparation 147 

dioxide, occurrence, properties 148 

use 149 

extraction .' 164, 141, 142 

occurrence, physical properties 141, 142, 163 

trioxide 150 

Sulphuric acid, manufacture of 151 

properties of 154 

pure 156 

Synthesis of water 69 

Tabasheer 117 

Tannin 368 

Tanning 433 

Tantalum 293 

Tapioca 377 

Tarter emetic 367 

Tellurium 160 

Temperature critical 172 

Terne-plate 295 

Terpenes 349 

Thallium 360 

Theihe 383 

Thermo-chemistry 201 

principles of 203 

Thenard's blue 289 

Thiosulphuric acid 158 

Thorium 296 

Tin, alloys of 295 

occurrence and reduction of 293 

oxides and salts of 296 

properties and uses 294 

Titanium 296 

Tungsten 292 

Turpentine 350 

Uranium 292 

Valency. 48 



458 INDEX. 

PAGE 

Valency and affinity contrasted 52 

of common elements 53 

variable 51 

Vanadin 292 

Vant Hoff 's solution law 182 

Vegetable casein 382 

colors 380 

fibrin 382 

Vinegar, preparation 364 

Volume relations of elements and compounds , 43 

Von Patera, silver reduction process 320 

Vulcanite 354 

Vulcanized rubber 353 

Water 74 

chemical properties 78 

Water composition, to determine 79 

contamination of 81 

deposits from . 83 

hard, action on soap 84 

and soft 82 

mineral „ . 85 

natural 80 

of crystallization 76 

constitution 77 

physical properties of 75 

purification of 85 

rain 80 

river and sea 85 

solvent power of , 75 

spring and well 81 

Washoe process 316 

Weights, equivalent 27 

atomic, table of 4 

Wine-making 423 

Wines, red 423 

White vitriol 253 

lead 304 

Whiskey, Bourbon 425 

Whiskies 425 

Wood spirit 426 

Xenon 169 

Yeast 357 



INDEX. 459 

PAGE 

Ziervogel method for working copper matte 313 

Zinc and its ores . , 250 

chloride 253 

hydroxide „ 254 

metallurgy of 250 

oxide of 253 

properties of 251 

salts, reactions of 254 

sulphate 253 

uses of 252 

Zirconium . . , , 296 



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Winton's Microscopy of Vegetable Foods 8vo, 7 50 

Woll's Handbook for Farmers and Dairymen i6mo, 1 50 



ARCHITECTURE. 

Baldwin's Steam Heating for Buildings nmo, 2 50 

Bashore's Sanitation of a Country House nmo, 1 00 

Berg's Buildings and Structures of American Railroads 4T0, 5 00 

Birkmire's Planning and Construction of American Theatres 8vo, 3 00 

Architectural Iron and Steel ". 8vo, 3 50 

Compound Riveted Girders as Applied in Buildings 8vo, 2 00 

Planning and Construction of High Office Buildings 8vo, 3 50 

Skeleton Construction in Buildings 8vo, 3 00 

Brigg's Modern American School Buildings 8vo, 4 00 

1 



Carpenter's Heating and Ventilating of Buildings 8vo, 

Freitag's Architectviral Engineering 8vo, 

Fireproofing of Steel Buildings 8vo, 

French and Ives's Stereotomy 8vo, 

Gerhard's Guide to Sanitary House-inspection iomo, 

Theatre Fires and Panics i2mo, 

♦Greene's Structural Mechanics 8vo, 

Holly's Carpenters' and Joiners' Handbook i8mo, 

Johnson's Statics by Algebraic and Graphic Methods 8vo, 

Kidder's Architects' and Builders' Pocket-book. Rewritten Edition. i6mo, mor., 
Merrill's Stones for Building and Decoration 8vo, 

Non-metallic Minerals : Their Occurrence and Uses 8vo, 

Monckton's Stair-building 4to, 

Patton's Practical Treatise on Foundations 8vo, 

Peabody's Naval Architecture 8vo, 

Rice's Concrete-block Manufacture 8vo, 

Richey's Handbook for Superintendents of Construction i6mo, mor., 

* Building Mechanics' Ready Reference Book. Carpenters' and Wood- 
workers' Edition i6mo, morocco, 

Sabin's Industrial and Artistic Technology of Paints and Varnish .8vo, 

Siebert and Biggin's Modern Stone-cutting and Masonry 8vo, 

Snow's Principal Species of Wood 8vo, 

Sondericker's Graphic Statics with Applications to Trusses, Beams, and Arches. 

8vo, 

Towne's Locks and Builders' Hardware i8mo, morocco, 

Wait's Engineering and Architectural Jurisprudence 8vo, 

Sheep, 

Law of Operations Preliminary to Construction in Engineering and Archi- 
tecture 8vo, 

Sheep, 

Law of Contracts 8vo, 

Wood's Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. .8vo, 

Worcester and Atkinson's Small Hospitals, Establishment and Maintenance, 

Suggestions for Hospital Architecture, with Plans for a Small Hospital. 

i2mo, 
The World's Columbian Exposition of 1893 Large 4to, 



ARMY AND NAVY. 

Bernadou's Smokeless Powder, Nitro-cellulose, and the Theory of the Cellulose 

Molecule i2mo, 

Chase's Screw Propellers and Marine Propulsion 8vo, 

Cloke's Gunner's Examiner 8vo, 

Craig's Azimuth 4 to, 

Crehore and Squier's Polarizing Photo-chronograph 8vo, 

* Davis's Elements of Law 8vo, 

* Treatise on the Military Law of United States 8vo, 

Sheep, 

De Brack's Cavalry Outposts Duties. (Carr.) 241110, morocco, 

Dietz's Soldier's First Aid Handbook i6mo, morocco, 

* Dudley's Military Law and the Procedure of Courts-martial. . . Large nmo, 
Durand's Resistance and Propulsion of Ships 8vo, 

* Dyer's Handbook of Light Artillery i2mo, 

Eissler's Modern High Explosives 8vo, 

* Fiebeger's Text-book on Field Fortification Small 8vo, 

Hamilton's The Gunner's Catechism i8mo, 

* HofFs Elementary Naval Tactics 8vo, 



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Ingalls's Handbook of Problems in Direct Fire. 8vo, 

* Ballistic Tables 8vo, 

* Lyons's Treatise on Electromagnetic Phenomena. Vols. I. and II. .8vo, each, 

* Mahan's Permanent Fortifications. (Mercur.) 8vo, half morocco, 

Manual for Courts-martial i6mo, morocco, 

* Mercur's Attack of Fortified Places i2mo, 

* Elements of the Art of War 8vo, 

Metcalf's Cost of Manufactures — And the Administration of Workshops. .8vo, 

* Ordnance and Gunnery. 2 vols i2mo, 

Murray's Infantry Drill Regulations „i8mo, paper, 

Nixon's Adjutants' Manual 24mo, 

Peabody's Naval Architecture 8vo, 

* Phelps's Practical Marine Surveying 8vo, 

Powell's Army Officer's Examiner i2mo, 

Sharpe's Art of Subsisting Armies in War i8mo, morocco, 

* Tupes and Poole's Manual of Bayonet Exercises and Musketry Fencing. 

24mo, leather, 

* Walke's Lectures on Explosives 8vo, 

Weaver's Military Explosives 8vo, 

* Wheeler's Siege Operations and Military Mining , .8vo, 

Winthrop's Abridgment of Military Law nmo, 

Woodhuil's Notes on Military Hygiene i6mo, 

Young's Simple Elements of Navigation i6mo, morocco, 

ASSAYING. 

Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. 

nmo, morocco, 

Furman's Manual of Practical Assaying 8vo, 

Lodge's Notes on Assaying and Metallurgical Laboratory Experiments. . . .8vo, 

Low's Technical Methods of Ore Analysis 8vo, 

Miller's Manual of Assaying i2mo, 

Cyanide Process i2mo, 

Minet's Production of Aluminum and its Industrial Use. (Waldo.) nmo, 

O'Driscoll's Notes on the Treatment of Gold Ores 8vo, 

Ricketts and Miller's Notes on Assaying 8vo, 

Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, 

Ulke's Modern Electrolytic Copper Refining 8vo, 

Wilson's Cyanide Processes nmo, 

Chlorination Process nmo, 



ASTRONOMY. 

Comstock's Fielf 1 Astronomy for Engineers 8vo, 2 50 

Craig's Azi~--»ui 4to, 3 50 

Crandall's Text-book on Geodesy and Least Squares 8vo, 3 00 

Doolittle's Treatise on Practical Astronomy 8vo, 4 00 

Gore's Elements of Geodesy 8vo, 2 50 

Hayford's Text-book of Geodetic Astronomy 8vo, 3 00 

Merriman's Elements of Precise Surveying and Geodesy 8vo, 2 50 

* Michie and Harlow's Practical Astronomy 8vo, 3 00 

* White's Elements of Theoretical and Descriptive Astronomy nmo 00 

BOTANY. 

Davenport's Statistical Methods, with Special Reference to Biological Variation. 

i6mo, morocco, 1 25 

Thomr and Bennett's Structural and Physiological Botany i6mo, 2 25 

Westermaier's Compendium of General Botany. (Schneider.) 8vo, 2 00 

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CHEMISTRY. 

* Abegg's Theory of Electrolytic Dissociation. (Von Ende.) i2mo, i 25 

Adriance's Laboratory Calculations and Specific Gravity Tables nmo. 1 25 

Alexeyeff's General Principles of Organic Synthesis. (Matthews.) 8vo, 3 00 

Allen's Tables for Iron Analysis 8vo, 3 00 

Arnold's Compendium of Chemistry. (Mandel.) Small 8vo, 3 50 

Austen's Notes for Chemical Students i2mo, 1 50 

Bernadou's Smokeless Powder.— Nitro-cellulose, and Theory of the Cellulose 

Molecule i2mo, 2 5a 

* Browning's Introduction to the Rarer Elements 8vo, 1 50 

Brush and Penfield's Manual of Determinative Mineralogy 8vo, 4 00 

* Claassen's Beet-sugar Manufacture. (Hall and Rolfe.) 8vo, 3 00 

Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.). .8vo, 3 00 

Cohn's Indicators and Test-papers i2mo, 2 00 

Tests and Reagents 8vo, 3 00 

Crafts's Short Course in Qualitative Chemical Analysis. (Schaeffer.). . .nmo, 1 50 

* Danneel's Electrochemistry. (Merriam.) i2mo, 1 25 

Dolezalek's Theory of the Lead Accumulator (Storage Battery). (Von 

Ende.) i2mo, 2 50 

Drechsel's Chemical Reactions. (Merrill.) i2mo, 1 25 

Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo, 4 00 

Eissler's Modern High Explosives 8vo, 4 o» 

Effront's Enzymes and their Applications. (Prescott.) 8vo, 3 00 

Erdmann's Introduction to Chemical Preparations. (Dunlap.) i2mo, 1 25 

Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. 

nmo, morocco, 1 50 

Fowler's Sewage Works Analyses nmo, 2 00 

Fresenius's Manual of Qualitative Chemical Analysis. (Wells.) 8vo, 5 00 

Manual of Qualitative Chemical Analysis. Part I. Descriptive. (Wells.) 8vo, 3 00 

Quantitative Chemical Analysis. (Cohn.) 2 vols. . 8vo, 12 50 

Fuertes's Water and Public Health nmo, 1 50 

Furman's Manual of Practical Assaying 8vo, 3 00 

* Getman's Exercises in Physical Chemistry i2mo, 2 00 

Gill's Gas and Fuel Analysis for Engineers nmo, 1 25 

* Gooch and Browning's Outlines of Qualitative Chemical Analysis. Small 8vo, 1 25 

Grotenfelt's Principles of Modern Dairy Practice. (Woll.) nmo, 2 00 

Groth's Introduction to Chemical Crystallography (Marshall) nmo, 1 25 

Hammarsten's Text-book of Physiological Chemistry. (Mandel.) 8vo, 4 00 

Helm's Principles of Mathematical Chemistry. (Morgan.). . . . , nmo, 1 50 

Hering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 

Herrick's Denatured or Industrial Alcohol. Fvo, 4 00 

Hind's Inorganic Chemistry 8vo, 3 00 

* Laboratory Manual for Students i2mo, 1 00 

Holleman's Text-book of Inorganic Chemistry. (Cooper.) 8vo, 2 50 

Text-book of Organic Chemistry. (Walker and Mott.) 8vo, 2 50 

* Laboratory Manual of Organic Chemistry. (Walker.) nmo, 1 00 

Hopkins's Oil-chemists' Handbook 8vo, 3 00 

Iddings's Rock Minerals 8vo, 5 00 

Jackson's Directions for Laboratory Work in Physiological Chemistry. .8vo, 1 25 

Keep's Cast Iron 8vo, 2 50 

Ladd's Manual of Quantitative Chemical Analysis nmo, 1 00 

Landauer's Spectrum Analysis. (Tingle.) .8vo, 3 00 

* Langworthy and Austen. The Occurrence of Aluminium in Vegetable 

Products, Animal Products, and Natural Waters 8vo p 2 00 

Lassar-Cohn's Application of Some General Reactions to Investigations in 

Organic Chemistry. (TingleO nmo, 1 00 

Leach's The Inspection and Analysis of Food with Special Reference to State 

Control 8vo, 7 50 

Lob's Electrochemistry of Organic Compounds. (Lorenz.). 8vo, 3 00 

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Lodge's Notes on Assaying and Metallurgical Laboratory Experiments. .. .8vo, 

Low's Technical Method of Ore Analysis 8vo, 

Lunge's Techno-chemical Analysis. (Conn.). . , i2mo 

* McKay and Larsen's Principles and Practice of Butter-making 8vo, 

Mandel's Handbook for Bio-chemical Laboratory i2mo, 

* Martin's Laboratory Guide to Qualitative Analysis with the Blowpipe . . i2mo, 
Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 

3d Edition, Rewritten 8vo, 

Examination of Water. (Chemical and Bacteriological.) i2mo, 

Matthew's The Textile Fibres. 2d Edition, Rewritten 8vo, 

Meyer's Determination of Radicles in Carbon Compounds. (Tingle.). . i2mo, 

Miller's Manual of Assaying i2mo, 

Cyanide Process i2mo, 

Minet's Production of Aluminum and its Industrial Use. (Waldo.) . . . . 121110, 

Mixter's Elementary Text-book of Chemistry i2mo, 

Morgan's An Outline of the Theory of Solutions and its Results 121110, 

Elements of Physical Chemistry i2mo, 

* Physical Chemistry for Electrical Engineers nmo, 

Morse's Calculations used in Cane-sugar Factories i6mo, morocco, 

* Muir's History of Chemical Theories and Laws . . . 8vo, 

Mulliken's General Method for the Identification of Pure Organic Compounds. 

Vol. I Large 8vo, 

O'Brine's Laboratory Guide in Chemical Analysis 8vo, 

O'Dnscoll's Notes on the Treatment of Gold Ores 8vo, 

Ostwald's Conversations on Chemistry. Part One. (Ramsey.) j2mo, 

Part Two. (Turnbull.) i2mo, 

* Pauli's Physical Chemistry in the Service of Medicine. ' (Fischer.) .... nmo, 

* Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 

8vo, paper , 

Pictet's The Alkaloids and their Chemical Constitution. (Biddle.) 8vo, 

Pinner's Introduction to Organic Chemistry. (Austen.) i2mo, 

Poole's Calorific Power of Fuels. . 8vo, 

Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- 
ence to Sanitary Water Analysis nmo, 

* Reisig's Guide to Piece-dyeing 8vo, ; 

Richards and Woodman's Air, Water, and Food from a Sanitary Standpoint.. 8vo, 
Ricketts and Russell's Skeleton Notes upon Inorganic Chemistry. (Part I. 

Non-metallic Elements.) 8vo, morocco, 

Ricketts and Miller's Notes on Assaying 8vo, 

Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 

Disinfection and the Preservation of Food 8vo, 

Riggs's Elementary Manual for the Chemical Laboratory 8vo, 

Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, 

Ruddiman's Incompatibilities in Prescriptions 8vo, 

* Whys in Pharmacy - i2mo, 

Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 

Salkowski's Physiological and Pathological Chemistry. (Orndorff.) 8vo, 

Schimpf's Text-book of Volumetric Analysis nmo, 

Essentials of Volumetric Analysis nmo, 

* Qualitative Chemical Analysis 8vo, 

Smith's Lecture Notes on Chemistry for Dental Students 8vo, 

Spencer's Handbook for Chemists of Beet-sugar Houses i6mo, morocco, 

Handbook for Cane Sugar Manufacturers i6mo, morocco, 

Stockbridge's Rocks and Soils 8vo, 

* Tillman's Elementary Lessons in Heat 8vo, 

* Descriptive General Chemistry 8vo, 

Treadwell's Qualitative Analysis. (Hall.) 8vo, 

Quantitative Analysis. (Hall.) 8vo, 

Turneaure and Russell's Public Water-supplies 8vo, 

5 



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Van Deventer's Physical Chemistry for Beginners. (Boltwood.) i2mo, 

* Walke's Lectures on Explosives 8vo, 

Ware's Beet-sugar Manufacture and Refining. Vol. I Small 8vo, 

Vol.11 SmallSvo, 

Washington's Manual of the Chemical Analysis of Rocks 8vo, 

Weaver's Military Explosives 8vo, 

Wehrenfennig's Analysis and Softening of Boiler Feed- Water 8vo, 

Wells's Laboratory Guide in Qualitative Chemical Analysis 8vo, 

Short Course in Inorganic Qualitative Chemical Analysis for Engineering 
Students nmo, 

Text-book of Chemical Arithmetic nmo, 

Whipple's Microscopy of Drinking-water 8vo, 

Wilson's Cyanide Processes nmo, 

Chlorination Process nmo, 

Winton's Microscopy of Vegetable Foods 8vo, 

Wulling's Elementary Course in Inorganic, Pharmaceutical, and Medical 
Chemistry nmo, 



CIVIL ENGINEERING. 

BRIDGES AND ROOFS. HYDRAULICS. MATERIALS OF ENGINEERING. 
RAILWAY ENGINEERING. 

Baker's Engineers' Surveying Instruments nmo, 3 oo 

Bixby's Graphical Computing Table Paper 10^X24! inches. 25 

Breed and Hosmer's Principles and Practice of Surveying 8vo, 3 00 

* Burr's Ancient and Modern Engineering and the Isthmian Canal 8vo, 3 50 

Comstock's Field Astronomy for Engineers 8vo, 2 50 

Crandall's Text-book on Geodesy and Least Squares 8vo, 3 00 

Davis's Elevation and Stadia Tables 8vo, 1 00 

Elliott's Engineering for Land Drainage nmo, 1 50 

Practical Farm Drainage nmo, 1 00 

*Fiebeger's Treatise on Civil Engineering 8vo, 5 00 

Flemer's Phototopographic Methods and Instruments .8vo, 5 00 

Folwell's Sewerage. (Designing and Maintenance.) 8vo, 3 00 

Freitag's Architectural Engineering. 2d Edition, Rewritten 8vo, 3 50 

French and Ives's Stereotomy 8vo, 2 50 

Goodhue's Municipal Improvements nmo, 1 50 

Gore's Elements of Geodesy 8vo, 2 50 

Hayford's Text-book of Geodetic Astronomy 8vo, 3 00 

Hering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 

Howe's Retaining Walls for Earth nmo, 1 25 

* Ives's Adjustments of the Engineer's Transit and Level i6mo, Bds. 25 

Ives and Hilts's Problems in Surveying i6mo, morocco, 1 50 

Johnson's (J. B.) Theory and Practice of Surveying Small 8vo, 4 00 

Johnson's (L. J.) Statics by Algebraic and Graphic Methods 8vo, 2 00 

Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.), nmo, 2 00 

Mahan's Treatise on Civil Engineering. (1873.) (Wood.) 8vo, 5 00 

* Descriptive Geometry 8vo, 1 50 

Merriman's Elements of Precise Surveying and Geodesy 8vo, 2 50 

Merriman and Brooks's Handbook for Surveyors i6mo, morocco, 2 00 

Nugent's Plane Surveying 8vo, 3 50 

Ogden's Sewer Design nmo, 2 00 

Parsons's Disposal of Municipal Refuse 8vo, 2 00 

Patton's Treatise on Civil Engineering 8vo half leather, 7 50 

Reed's Topographical Drawing and Sketching 4to, 5 00 

Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 4 00 

Siebert and Biggin's Modern Stone-cutting and Masonry 8vo, 1 50 



2 


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6 


50 


5 


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2 


50 


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25 


3 


50 



Smith's Manual 01 Topographical Drawing. (McMillan.) 8vo, 2 50 

Sondericker's Graphic Statics, with Applications to Trusses, Beams, and Arches. 

8vo, 

Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 

* Trautwine's Civil Engineer's Pocket-book i6mo, morocco, 

Venable's Garbage Crematories in America 8vo, 

Wait's Engineering and Architectural Jurisprudence 8vo 

Sheep, 
Law of Operations Preliminary to Construction in Engineering and Archi- 
tecture 8vo, 

Sheep, 

Law of Contracts 8vo, 

Warren's Stereotomy — Problems in Stone-cutting 8vo, 

Webb's Problems in the Use and Adjustment of Engineering Instruments. 

i6mo, morocco, 
Wilson's Topographic Surveying 8vo, 



BRIDGES AND ROOFS. 

Boiler's Practical Treatise on the Construction of Iron Highway Bridges. .8vo, 2 00 

* Thames River Bridge 4to, paper, 5 00 

Burr's Course on the Stresses in Bridges and Roof Trusses, Arched Ribs, and 

Suspension Bridges 8vo, 3 50 

Burr and Falk's Influence Lines for Bridge and Roof Computations 8vo, 3 00 

Design and Construction of Metallic Bridges 8vo 5 00 

Du Bois's Mechanics of Engineering. Vol. II Small 4to, 10 00 

Foster's Treatise on Wooden Trestle Bridges 4to, 5 00 

Fowler's Ordinary Foundations 8vo, 3 50 

Greene's Roof Trusses 8vo, 1 25 

Bridge Trusses 8vo, 2 50 

Arches in Wood, Iron, and Stone 8vo 2 50 

Howe's Treatise on Arches 8vo, 4 00 

Design of Simple Roof-trusses in Wood and Steel ,. 8vo, 2 00 

Symmetrical Masonry Arches 8vo, 2 50 

Johnson, Bryan, and Turneaure's Theory and Practice in the Designing of 

Modern Framed Structures Small 410, 10 00 

Merriman and Jacoby's Text-book on Roofs and Bridges : 

Pari L Stresses in Simple Trusses 8vo, 2 50 

Part IL Graphic Statics 8vo, 2 50 

Fart III. Bridge Design 8vo, 2 50 

Part IV. Higher Structures 8vo, 2 50 

Morison's Memphis Bridge 4to, 10 00 

Waddell's De Pontibus, a Pocket-book for Bridge Engineers. . i6mo, morocco, 2 00 

* Specifications for Steel Bridges i2mo, 50 

Wright's Designing of Draw-spans. Two parts in one volume 8vo, 3 5<> 



HYDRAULICS. 

Barnes's Ice Formation 8vo, 3 00 

Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from 

an Orifice. (Trautwine.) 8vo> 2 00 

Bovey's Treatise on Hydraulics 8vo, 5 00 

Church's Mechanics of Engineering 8vo, 6 00 

Diagrams of Mean Velocity of Water in Open Channels paper, 1 50 

Hydraulic Motors 8vo, 2 00 

Coffin's Graphical Solution of Hydrr.ulic Problems i6mo, morocco, 2 50 

Flather's Dynamometers, and the Measurement of Power i2mo, 3 00 

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Folwell's Water-supply Engineering 8vo, 

Frizell's Water-power 8vo, 

Fuertes's Water and Public Health nmo, 

Water-filtration Works i2mo, 

Ganguillet and Kutter's General Formula for the Uniform Flow of Water in 

Rivers and Other Channels. (Hering and Trautwine.) 8vo, 

Hazen's Filtration of Public Water-supply 8vo, 

Hazlehurst's Towers and Tanks for Water-works 8vo, 

Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal 

Conduits 8vo, 2 00 

Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 

8vo, 4 00 
Merriman's Treatise on Hydraulics 8vo, 5 00 

* Michie's Elements of Analytical Mechanics 8vo, 4 00 

Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- 
supply Large 8vo, 5 00 

* Thomas and Watt's Improvement of Rivers 4to, 6 00 

Turneaure and Russell's Public Water-supplies 8vo, 5 00 

Wegmann's Design and Construction of Dams 4x0, 5 00 

Water-supply of the City of New York from 1658 to 1805 4to, 10 00 

Whipple's Value of Pure Water Large nmo, 1 00 

Williams and Hazen's Hydraulic Tables 8vo, 1 50 

Wilson's Irrigation Engineering Small 8vo, 4 00 

Wolff's Windmill as a Prime Mover 8vo, 3 00 

Wood's Turbines 8vo, 2 50 

Elements of Analytical Mechanics 8vo, 3 00 



MATERIALS OF ENGINEERING. 

Baker's Treatise on Masonry Construction 8vo, 

Roads and Pavements 8vo, 

Black's United States Public Works Oblong 410, 

* Bovey's Strength of Materials and Theory of Structures 8vo, 

Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 

Byrne's Highway Construction 8vo, 

Inspection of the Materials and Workmanship Employed in Construction. 

i6mo, 

Church's Mechanics of Engineering.. 8vo, 

Du Bois's Mechanics-of Engineering. Vol. I. Small 4to, 

"♦Eckel's Cements, Limes, and Plasters 8vo, 

Johnson's Materials of Construction Large 8vo, 

Fowler's Ordinary Foundations : 8vo, 

Graves's Forest Mensuration 8vo, 

* Greene's Structural Mechanics 8vo, 

Keep's Cast Iron 8vo, 

Lanza's Applied Mechanics. 8vo, 

Marten's Handbook on Testing Materials. (Henning.) 2 vols 8vo, 

Maurer's Technical Mechanics 8vo, 

Merrill's Stones for Building and Decoration 8vo, 

Merriman's Mechanics of Materials 8vo, 

* Strength of Materials nmo, 

Metcalf' s Steel. A Manual for Steel-users nmo, 

Patton's Practical Treatise on Foundations 8vo, 

Richardson's Modern Asphalt Pavements 8vo, 

Richey's Handbook for Superintendents of Construction i6mo, mor., 

* Ries's Clays: Their Occurrence, Properties, and Uses 8vo, 

Rockwell's Roads and Pavements in France nmo, 



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Sabin's Industrial and Artistic Technology of Paints and Varnish „8vo, 

* Schwarz's Longleaf Pine in Virgin Forest i2mo, 

Smith's Materials of Machines i2mo, 

Snow's Principal Species of Wood 8vo, 

Spalding's Hydraulic Cement i2mo, 

Text-book on Roads and Pavements i2mo, 

Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 

Thurston's Materials of Engineering. 3 Parts 8vo, 

Part I. Non-metallic Materials of Engineering and Metallurgy 8vo, 

Part II. Iron and Steel 8vo, 

Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents 8vo, 

Tillson's Street Pavements and Paving Materials 8vo, 

Waddell's De Pontibus. (A Pocket-book for Bridge Engineers.) . . i6mo, mor., 

* Specifications for Steel Bridges . nmo, 

Wood's (De V.) Treatise on the Resistance of Materials, and an Appendix on 

the Preservation of Timber 8vo, 

Wood's (De V.) Elements of Analytical Mechanics 8vo, 

Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and 

Steel 8vo, 4 00 



RAILWAY ENGINEERING. 

Andrew's Handbook for Street Railway Engineers 3x5 inches, morocco, 1 25 

Berg's Buildings and Structures of American Railroads 4to, 5 00 

Brook's Handbook of Street Railroad Location i6mo, morocco, 1 50 

Butt's Civil Engineer's Field-book i6mo, morocco, 2 50 

Crandall's Transition Curve i6mo, morocco, 1 50 

Railway and Other Earthwork Tables 8vo, 1 50 

Dawson's "Engineering" and Electric Traction Pocket-book. . i6mo, morocco, 5 00 

Dredge's History of the Pennsylvania Railroad: (1879) Paper, 5 00 

Fisher's Table of Cubic Yards Cardboard, 25 

Godwin's Railroad Engineers' Field-book and Explorers' Guide . . . i6mo, mor., 2 50 
Hudson's Tables for Calculating the Cubic Contents of Excavations and Em- 
bankments 8vo, 1 00 

Molitor and Beard's Manual for Resident Engineers i6mo, 1 00 

Nagle's Field Manual for Railroad Engineers i6mo, morocco, 3 00 

Philbrick's Field Manual for Engineers i6mo, morocco, 3 00 

Searles's Field Engineering i6mo, morocco, 3 00 

Railroad Spiral i6mo, morocco, 1 50 

Taylor's Prismoidal Formula? and Earthwork 8vo, 1 50 

* Trautwine's Method of Calculating the Cube Contents of Excavations and 

Embankments by the Aid of Diagrams 8vo, 2 00 

The Field Practice of Laying Out Circular Curves for Railroads. 

nmo, morocco, 2 50 

Cross-section Sheet Paper, 25 

Webb's Railroad Construction i6mo, morocco, 5 00 

Economics of Railroad Construction Large nmo, 2 50 

Wellington's Economic Theory of the Location of Railways Small 8vo, 5 00 



DRAWING. 

Barr's Kinematics of Machinery 8vo, 2 50 

* Bartlett's Mechanical Drawing 8vo, 3 00 

* " " '* Abridged Ed 8vo, 150 

Coolidge's Manual of Drawing 8vo, paper, 1 00 



Coolidge and Freeman's Elements of General Drafting for Mechanical Engi- 
neers Obiong 4to, 

Durley's Kinematics of Machines 8vo, 

Emch's Introduction to Projective Geometry and its Applications 8vo, 

Hill's Text-book on Shades and Shadows, and Perspective. . .„ 8vo, 

Jamison's Elements of Mechanical Drawing 8vo, 

Advanced Mechanical Drawing 8vo, 

Jones's Machine Design: 

Part I. Kinematics of Machinery 8vo, 

Part II. Form, Strength, and Proportions of Parts 8vo, 

MacCord's Elements of Descriptive Geometry 8vo, 

Kinematics ; or, Practical Mechanism 8vo, 

Mechanical Drawing 4to, 

Velocity Diagrams 8vo, 

MacLeod's Descriptive Geometry Small 8vo, 

* Mahan's Descriptive Geometry and Stone-cutting 8vo, 

Industrial Drawing. (Thompson.) 8vo, 

Moyer's Descriptive Geometry 8vo, 

Reed's Topographical Drawing and Sketching 4to, 

Reid's Course in Mechanical Drawing 8vo, 

Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 

Robinson's Principles of Mechanism 8vo, 

Schwamb and Merrill's Elements of Mechanism 8vo, 

Smith's (R. S.) Manual of Topographical Drawing. (McMillan.) 8vo, 

Smith (A. W.) and Marx's Machine Design 8vo, 

* Titsworth's Elements of Mechanical Drawing Oblong 8vo, 

Warren's Elements of Plane and Solid Free-hand Geometrical Drawing, nmo, 

Drafting Instruments and Operations i2mo, 

Manual of Elementary Projection Drawing nmo, 

Manual of Elementary Problems in the Linear Perspective of Form and 

Shadow i2mo, 

Plane Problems in Elementary Geometry i2mo, 

Primary Geometry. nmo, 

Elements of Descriptive Geometry, Shadows, and Perspective 8vb, 

General Problems of Shades and Shadows 8vo, 

Elements of Machine Construction and Drawing . .8vo, 

Problems, Theorems, and Examples in Descriptive Geometry 8vo, 

Weisbach's Kinematics and Power of Transmission. (Hermann and 

Klein.) 8vo, 

Whelpley's Practical Instruction in the Art of Letter Engraving. ...... nmo, 

Wilson's (H. M.) Topographic Surveying ■ 8vo, 

Wilson's (V. T.) Free-hand Perspective 8vo, 

Wilson's (V. T.) Free-hand Lettering 8vo, 

Woolf's Elementary Course in Descriptive Geometry Large 8vo, 



ELECTRICITY AND PHYSICS. 

* Abegg's Theory of Electrolytic Dissociation. (Von Ende.) nmo, i 25 

Anthony and Brackett's Text-book of Physics. (Magie.) Small 8vo 3 00 

Anthony's Lecture-notes on the Theory of Electrical Measurements. . . . nmo, 1 00 

Benjamin's History of Electricity 8vo, 3 00 

Voltaic Cell 8vo, 3 00 

Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.).8vo, 3 00 

* Collins's Manual of Wireless Telegraphy nmo, 1 50 

Morocco, 2 00 

Crehore and Squier's Polarizing Photo-chronograph 8vo, 3 00 

* Danneel's Electrochemistry. (Merriam.) nmo, 1 25 

Dawson's "Engineering" and Electric Traction Pocket-book. i6mo, morocco, 5 00 

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Dolezalek's Theory of the Lead Accumulator (Storage Battery). (Von 

Ende. ) i2mo, 2 50 

Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo, 4 00 

Flather's Dynamometers, and the Measurement of Power i2mo, 3 00 

Gilbert's De Magnete. (Mottelay.) 8vo, 2 50 

Hanchett's Alternating Currents Explained i2mo, 1 00 

Hering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 

Holman's Precision of Measurements 8vo, 2 00 

Telescopic Mirror-scale Method, Adjustments, and Tests. . . .Large 8vo, 75 

Kinzbrunner's Testing of Continuous-current Machines 8vo, 2 00 

Landauer's Spectrum Analysis. (Tingle.) 8vo, 3 00 

Le Chateliers High-temperature Measurements. (Boudouard — Burgess.) i2mo, 3 00 

Lob's Electrochemistry of Organic Compounds. (Lorenz.) 8vo, 3 00 

* Lyons'? Treatise on Electromagnetic Phenomena. Vols. I. and II. 8vo, each, 6 00 

* Michie's Elements of Wave Motion Relating to Sound and Light 8vo, 4 00 

Niaudet's Elementary Treatise on Electric Batteries. (Fishback.) nmo, 2 50 

* Parshall and Hobart's Electric Machine Design 4to, half morocco, 12 50 

Reagan's Locomotives: Simple, Compound, and Electric. New Edition. 

Large i2mo, 3 50 

* Rosenberg's Electrical Engineering. (Haldane Gee — Kinzbrunner.). . .8vo, 2 00 

Ryan, Norris, and Hoxie's Electrical Machinery. Vol. 1 8vo, 2 50 

Thurston's Stationary Steam-engines 8vo, 2 30 

* Tillman's Elementary Lessons in Heat 8vo, 1 50 

Tory and Pitcher's Manual of Laboratory Physics Small 8vo, 2 00 

Ulke's Modern Electrolytic Copper Refining 8vo, 3 00 



LAW. 

* Davis's Elements of Law 8vo, 

* Treatise on the Military Law of United States 8vo, 

* Sheep, 

* Dudley's Military Law and the Procedure cf Courts-martial . . . .Large i2mo, 

Manual for Courts-martial i6mo, morocco, 

Wait's Engineering and Architectural Jurisprudence 8vo, 

Sheep, 
Law of Operations Preliminary to Construction in Engineering and Archi- 
tecture 8vo 

Sheep, 

Law of Contracts 8vo, 

Winthrop's Abridgment of Military Law i2mo, 



MANUFACTURES. 

Bernadou's Smokeless Powder — Nitro-cellulose and Theory of the Cellulose 

Molecule i2mo, 

Bolland's Iron Founder i2mo, 

The Iron Founder," Supplement i2mo, 

Encyclopedia of Founding and Dictionary of Foundry Terms Used in the 
Practice of Moulding i2mo, 

* Claassen's Beet-sugar Manufacture. (Hall and Rolfe.) 8vo, 

* Eckel's Cements, Limes, and Plasters 8vo, 

Eissler's Modern High Explosives 8vo, 

Effront's Enzymes and their Applications. (Prescott.) 8vo, 

Fitzgerald's Boston Machinist nmo, 

Ford's Boiler Making for Boiler Makers i8mo, 

Herric't's Denatured or Industrial Alcohol Svo, 

Hopkin's Oil-chemists' Handbook 8vo, 

Keep's Cast Iron 8vo, 

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Reach's The Inspection and Analysis of Food with Special Reference to State 

Control. Large 8vo, 7 50 

* McKay and Larsen's Principles and Practice of Butter-making 8vo, 1 50 

Matthews's The Textile Fibres. 2d Edition, Rewritten 8vo , 4 00 

Metcalf's SteeL A Manual for Steel-users i2mo, 2 00 

Metcalfe V Cost of Manufactures — And the Administration of Workshops. 8vo, 5 00 

Meyer's Modern Locomotive Construction 4to, 10 00 

Morse's Calculations used in Cane-sugar Factories i6mo, morocco, 1 50 

* Reisig's Guide to Piece-dyeing, 8vo, 25 00 

Rice's Concrete-block Manufacture 8vo, 2 00 

Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 00 

Smith's Press-working of Metals , 8vo, 3 00 

Spalding's Hydraulic Cement i2mo ; 2 00 

Spencer's Handbook for Chemists of Beet-sugar Houses. .... i6mo morocco, 3 00 

Handbook for Cane Sugar Manufacturers i6mo morocco, 3 00 

Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 5 00 

Thurston's Manual of Steam-boilers, their Designs, Construction and Opera- 
tion 8vo, 5 00 

* Walke's Lectures on Explosives 8vo, 4 00 

Ware's Beet-sugar Manufacture and Refining. Vol.1 Small 8vo, 400 

Vol. II 8vo, 5 00 

Weaver's Military Explosives .8vo, 3 00 

West's American Foundry Practice i2mo, 2 50 

Moulder's Text-book , i2mo, 2 50 

Wolff's Windmill as a Prime Mover .8vo, 3 00 

Wood's Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. .8vo, 4 00 



MATHEMATICS. 

Baker's Elliptic Functions. c . = 8vo, 

* Bass's Elements of Differential Calculus. i2mo, 

Briggs's Elements of Plane Analytic Geometry . i2mo, 

Compton's Manual of Logarithmic Computations i2mo 

Davis's Introduction to the Logic of Algebra 8vo, 

* Dickson's College Algebra Large i2mo ; 

* Introduction to the Theory of Algebraic Equations. , Large i2mo, 

Emch's Introduction to Projective Geometry and its Applications.. 8vo 

Halsted's Elements of Geometry 8vo, 

Elementary Synthetic Geometry.. ■. 8vo, 

* Rational Geometry nmo, 

* Johnson's (J. B.) Three-place Logarithmic Tables: Vest-pocket size. paper, 

100 copies for 

* Mounted on heavy cardboard, 8X 10 inches, 

10 copies for 
Johnson's (W. W.) Elementary Treatise on Differential Calculus . . Small 8vo, 

Elementary Treatise on the Integral Calculus Small*8vo, 

Johnson's (W. W.) Curve Tracing in Cartesian Co-ordinates, i2mo, 

Johnson's (W. W.) Treatise on Ordinary and Partial* Differential Equations. 

Small 8vo, 
Johnson's (W. W.) Theory of Errors and the Method of Least Squares. i2mo, 

* Johnson's (W. W.) Theoretical Mechanics nmo, 

Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.) . nmo, 

* Ludlow and Bass. Elements of Trigonometry and Logarithmic and Other 

Tables 870, 

Trigonometry and Tables published separately Etch, 

* Ludlow's Logarithmic and Trigonometric Tables, Svo 

Manning's Irrational Numbers and their Representation by Sequences and Series 

j2rno, 1 25 
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Mathematical Monographs. Edited by Mansfield Merriman and Robert 

S. Woodward Octavo, each i oo 

Wo. i. History of Modern Mathematics, by David Eugene Smith. 
Wo. 2. Synthetic Projective Geometry, by George Bruce Halsted. 
Wo. 3. Determinants, by Laenas Gifford Weld. Wo. 4. Hyper- 
bolic Functions, by James McMahon. Wo. 5. Harmonic Func- 
tions, by William E. Byerly. Wo. 6. Grassmann's Space Analysis, 
T)y Edward W. Hyde. Wo. 7. Probability and Theory of Errors, 
hy Robert S. Woodward. Wo. 8. Vector Analysis and Quaternions, 
by Alexander Macfarlane. Wo. 9. Differential Equations, by 
William Woolsey Johnson. Wo. 10. The Solution of Equations, 
by Mansfield Merriman. Wo. 11. Functions of a Complex Variable, 
by Thomas S. Fiske. 

Maurer's Technical Mechanics 8vo, 4 00 

Merriman's Method of Least Squares 8vo, 2 00 

Rice and Johnson's Elementary Treatise on the Differential Calculus. . Sm. 8vo, 3 00 

Differential and Integral Calculus. 2 vols, in one Small 8vo, 2 50 

* Veblen and Lennes's Introduction to the Real Infinitesimal Analysis of One 

Variable : . . . 8vo, 2 00 

Wood's Elements of Co-ordinate Geometry 8vo, 2 00 

Trigonometry: Analytical, Plane, and Spherical nmo, 1 00 



MECHANICAL ENGINEERING. 

MATERIALS OF EWGIWEERIWG, STEAM-EWGIWES AWD BOILERS. 

Bacon's Forge Practice nmo, 

Baldwin's Steam Heating for Buildings nmo, 

Barr's Kinematics of Machinery 8vo, 

* Bartlett's Mechanical Drawing. 8vo, 

* " " " Abridged Ed 8vo, 

Benjamin's Wrinkles and Recipes nmo, 

Carpenter's Experimental Engineering 8vo, 

Heating and Ventilating Buildings 8vo, 

Clerk's Gas and Oil Engine Small 8vo, 

Coolidge's Manual of Drawing 8vo, paper, 

Coolidge and Freeman's Elements of General Drafting for Mechanical En- 
gineers Oblong 4to, 

Cromwell's Treatise on Toothed Gearing nmo, 

Treatise on Belts and Pulleys nmo, 

Durley's Kinematics of Machines 8vo, 

Flather's Dynamometers and the Measurement of Power. nmo, 

Rope Driving nmo, 

Gill's Gas and Fuel Analysis for Engineers nmo, 

Hall's Car Lubrication nmo, 

Hering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 

Hutton's The Gas Engine, 8vo, 

Jamison's Mechanical Drawing 8vo, 

Jones's Machine Design: 

Part I. Kinematics of Machinery 8vo, 

Part II. Form, Strength, and Proportions of Parts 8vo, 

Kent's Mechanical Engineers' Pocket-book. . i6mo, morocco, 

Kerr's Power and Power Transmission 8vo, 

Leonard's Machine Shop, Tools, and Methods 8vo, 

* Lorenz's Modern Refrigerating Machinery. (Pope, Haven, and Dean.) . . 8vo, 
MacCord's Kinematics; or, Practical Mechanism 8vo, 

Mechanical Drawing 410, 

Velocity Diagrams 8vo, 

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MacFarland's Standard Reduction Factors for Gases 8vo, 

Mahan's Industrial Drawing. (Thompson.) 8vo, 

Poole's Calorific Power of Fuels 8vo, 

Reid's Course in Mechanical Drawing 8vo, 

Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 

Richard's Compressed Air nmo, 

Robinson's Principles of Mechanism 8vo, 

Schwamb and Merrill's Elements of Mechanism 8vo, 

Smith's (O.) Press-working of Metals 8vo, 

Smith (A. W.) and Marx's Machine Design 8vo, 

Thurston's Treatise on Friction and Lost Work in Machinery and Mill 

Work 8vo, 

Animal as a Machine and Prime Motor, and the Laws of Energetics. i2mo, 

Tillson's Complete Automobile Instructor i6mo, 

Morocco, 2 00 

Warren's Elements of Machine Construction and Drawing 8vo, 7 50 

Weisbach's Kinematics and the Power of Transmission. (Herrmann — 

Klein. ) 8vo, 5 00 

Machinery of Transmission and Governors. (Herrmann — Klein.). .8vo, 5 00 

Wolff's Windmill as a Prime Mover 8vo, 3 00 

Wood's Turbines 8vo, 2 50 

MATERIALS OF ENGINEERING. 

* Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 

Burr's Elasticity and Resistance of the Materials of Engineering. 6th Edition. 

Reset 8vo, 

Church's Mechanics of Engineering 8vo, 

* Greene's Structural Mechanics , .8vo, 

Johnson's Materials of Construction 8vo, 

Keep's Cast Iron 8vo, 

Lanza's Applied Mechanics 8vo, 

Martens's Handbook on Testing Materials. (Henning.) 8vo, 

Maurer's Technical Mechanics 8vo, 

Merriman's Mechanics of Materials .8vo, 

* Strength of Materials i2mo, 

Metcalf's Steel. A Manual for Steel-users nmo, 

Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 

Smith's Materials of Machines i2mo, 

Thurston's Materials of Engineering 3 vols., 8vo, 

Part II. Iron and Steel 8vo, 

Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents 8vo, 2 50 

Wood's (De V.) Treatise on the Resistance of Materials and an Appendix on 

the Preservation of Timber 8vo, 2 00 

Elements of Analytical Mechanics .8vo, 3 00 

Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and 

Steel 8vo, 4 00 

STEAM-ENGINES AND BOILERS. 

Berry's Temperature-entropy Diagram i2mo, 1 25 

Carnot's Reflections on the Motive Power of Heat. (Thurston.) nmo, 1 50 

Creighton's Steam-engine and other Heat-motors — 8vo, 5 00 

Dawson's "Engineering" and Electric Traction Pocket-book. . . ,i6mo, mor., 5 00 

Ford's Boiler Making for Boiler Makers i8mo, 1 00 

Goss's Locomotive Sparks 8vo, 2 00 

Locomotive Performance 8vo, 5 00 

Hemenway's Indicator Practice and Steam-engine Economy i2mo, 2 00 

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Hutton's Mechanical Engineering of Power Plants 8vo, 5 00 

Heat and Heat-engines. . . : 8vo ; 5 00 

Kent's Steam boiler Economy 8vo, 4 00 

Kneass'i Practice and Theory of the Injector 8vo, 1 50 

MacCord's Slide-valves 8vo, 2 00 

Meyer's Modern Locomotive Construction 4to, 10 oc 

Peabody's Manual of the Steam-engine Indicator i2mo, i 50 

Tables of the Properties of Saturated Steam and Other Vapors 8vo, 1 00 

Thermodynamics of the Steam-engine and Other Heat-engines 8vo, 5 00 

Valve-gears for Steam-engines 8vo, 2 50 

Peabody and Miller's Steam-boilers 8vo, 4 00 

Pray's Twenty Years with the Indicator Large 8vo, 2 50 

Pupin's Thermodynamics of Reversible Cycles in Gases and Saturated Vapors. 

(Osterberg.) nmo, 1 25 

Reagan's Locomotives: Simple, Compound, and Electric. New Edition. 

Large i2mo, 3 50 

Rontgen's Principles of Thermodynamics. (Du Bois.). 8vo, 5 oc 

Sinclair's Locomotive Engine Running and Management nmo, 2 00 

Smart's Handbook of Engineering Laboratory Practice i2mo, 2 50 

Snow's Steam-boiler Practice '. .8vo, 3 00 

Spangler's Valve-gears 8vo, 2 50 

Notes on Thermodynamics nmo, 1 00 

Spangler, Greene, and Marshall's Elements of Steam-engineering 8vo, 3 00 

Thomas's Steam-turbines 8vo, 3 50 

Thurston's Handy Tables 8vo, 1 50 

Manual of the Steam-engine 2 vols., 8vo, 10 00 

Part I. History, Structure, and Theory 8vo, 6 00 

Part II. Design, Construction, and Operation 8vo, 6 00 

Handbook of Engine and Boiler Trials, and the Use of the Indicator and 

the Prony Brake 8vo, 5 00 

Stationary Steam-engines 8vo, 2 50 

Steam-boiler Explosions in Theory and in Practice nmo, 1 50 

Manual of Steam-boilers, their Designs, Construction, and Operation. 8vo, 5 00 

Wehrenfenning's Analysis and Softening of Boiler Feed-water (Patterson) 8vo, 4 00 

Weisbach's Heat, Steam, and Steam-engines. (Du Bois.) 8vo, 5 00 

Whitham's Steam-engine Design 8vo, 5 00 

Wood's Thermodynamics, Heat Motors, and Refrigerating Machines. . .8vo, 4 00 



2 50 



MECHANICS AND MACHINERY. 

Barr's Kinematics of Machinery 8vo 

* Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 

Chase's The Art of Pattern-making nmo, 2 50 

Church's Mechanics of Engineering 8vo, 6 00 

Notes and Examples in Mechanics 8vo, 2 00 

Compton's First Lessons in Metal- working i2mo, 1 50 

Compton and De Groodt's The Speed Lathe nmo, 1 50 

Cromwell's Treatise on Toothed Gearing nmo, 1 50 

Treatise on Belts and Pulleys nmo, 1 50 

Dana's Text-book of Elementary Mechanics for Colleges and Schools, .nmo, 1 50 

Dingey's Machinery Pattern Making nmo, 2 00 

Dredge's Record of the Transportation Exhibits Building of the World's 

Columbian Exposition of 1893 4to half morocco, 5 00 

Du Bois's Elementary Principles of Mechanics: 

Vol. I. Kinematics 8vo, 

Vol. H. Statics .8vo. 

Mechanics of Engineering. Vol. I Small 4to, 

Vol. II Small 4to, 

Durley's Kinematics of Machines 8vo, 

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Fitzgerald's Boston Machinist i6mo, i oo> 

Flather's Dynamometers, and the Measurement of Power i2mo, 3 oo- 

Rope Driving nmo, 2 00 

Goss's Locomotive Sparks 8vo, 2 00 

Locomotive Performance 8vo, 5 00 

* Greene's Structural Mechanics 8vo, 2 5a 

Hall's Car Lubrication nmo, 1 00 

Holly's Art of Saw Filing i8mo, 75 

James's Kinematics of a Point and the Rational Mechanics of a Particle. 

Small 8vo, 2 oa 

* Johnson's (W. W.) Theoretical Mechanics nmo, 3 00 

Johnson's (L. J.) Statics by Graphic and Algebraic Methods 8vo, 2 00 

Jones's Machine Design: 

Part I. Kinematics of Machinery 8vo, 1 50- 

Part H. Form, Strength, and Proportions of Parts 8vo, 3 00 

Kerr's Power and Power Transmission 8vo, 2 00- 

Lanza's Applied Mechanics 8vo, 7 50 

Leonard's Machine Shop, Tools, and Methods 8vo, 4 00- 

* Lorenz's Modern Refrigerating Machinery. (Pope, Haven, and Dean.). 8vo, 4 00 
MacCord's Kinematics; or, Practical Mechanism 8vo, 5 00 

Velocity Diagrams 8vo, 1 50 

* Martin's Text Book on Mechanics, Vol. I, Statics nmo, 1 25 

Maurer's Technical Mechanics 8vo, 4 00 

Merriman's Mechanics of Materials 8vo, 5 00 

* Elements of Mechanics nmo, 1 00 

* Michie's Elements of Analytical Mechanics 8vo, 4 00 

* Parshall and Hobart's Electric Machine Design 4to,half mr ^cco, 12 50 

Reagan's Locomotives: Simple, Compound, and Electric. New Edition. 

Large nmo, 3 00 

Reid's Course in Mechanical Drawing 8vo, 2 00 

Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 3 00 

Richards's Compressed Air nmo, 1 50 

Robinson's Principles of Mechanism 8vo, 3 00 

Ryan, Norris, and Hoxie's Electrical Machinery. Vol. 1 8vo, 2 50 

Sanborn's Mechanics : Problems Large nmo, 1 50 

Schwamb and Merrill's Elements of Mechanism .8vo, 3 00 

Sinclair's Locomotive-engine Running and Management nmo, 2 00 

Smith's (O.) Press-working of Metals 8vo, 3 00 

Smith's (A. W.) Materials of Machines nmo, 1 00 

Smith (A. W.) and Marx's Machine Design 8vo, 3 00 

Spangler, Greene, and Marshall's Elements of Steam-engineering.. 8vo, 3 00 

Thurston's Treatise on Friction and Lost Work in Machinery and Mill 

Work 8vo, 3 oo- 

Animal as a Machine and Prime Motor, and the Lawc of Energetics, nmo, 1 00 

Tillson's Complete Automobile Instructor i6mo, 1 50- 

Morocco, 2 oo- 

Warren's Elements of Machine Construction and Drawing 8vo, 7 50 

Weisbach's Kinematics and Power of Transmission. (Herrmann — Klein.). 8vo, 5 00- 

Machinery of Transmission and Governors. (Herrmann — Klein. ).8vo, 5 o* 

Wood's Elements of Analytical Mechanics 8vo, 3 00- 

Piinciples of Elementary Mechanics nmo, 1 25. 

Turbines. . 8vo, 2 50 

The World's Columbian Exposition of 1893 .4to, 1 oo- 

MEDICAL. 

De Fursac's Manual of Psychiatry. (Rosanoff and Collins.) Large nmo, 2 50- 

Ehrlich's Collected Studies on Immunity. (Bolduan.) 8vo, 6 oo> 

Hammarsten's Text-book on Physiological Chemistry. (Mandel.) 8vo, 4 oa 

16 



Lassar-Cohn's Practical Urinary Analysis. (Lorenz.) nmo, 

* Pauli's Physical Chemistry in the Service of Medicine. (Fischer.) . . . . i2mo, 

* Pozzi-Escot's The Toxins and Venoms and their Antibodies. (Cohn.). i2mo, 

Rostoski's Serum Diagnosis. (Bolduan.) i2mo, 

Salkowski's Physiological and Pathological Chemistry. (Orndorff.) 8vo, 

* Satterlee''* OutUnes of Human Embryology i2mo, 

Steel's Treatise on the Diseases of the Dog 8vo, 

Von Behring's Suppression of Tuberculosis. (Bolduan.) i2mo, 

Wassermann's Immune Sera : Haemolysis, Cytotoxins, and Precipitins. (Bol- 
duan.) i2mo, cloth, 

WoodhulTs Notes on Military Hygiene i6mo, 

* Personal Hygiene i2mo, 

Wulling's An Elementary Course in Inorganic Pharmaceutical and Medical 
Chemistry i2mo, 



METALLURGY. 

Egleston's Metallurgy of Silver, Gold, and Mercury: 

Vol. I. Silver 8vo, 

Vol. II. Gold and Mercury 8vo, 

Goesel's Minerals and Metals: A Reference Book , . . . . i6mo, mor. 

* Iles's Lead-smelting nmo, 

Keep's Cast Iron 8vo, 

Kunhardt's Practice of Ore Dressing in Europe 8vo, 

Le Chatelier's High-temperature Measurements. (Boudouard — Burgess. )i2mo, 

Metcalf's Steel. A Manual for Steel-users nmo, 

Miller's Cyanide Process i2mo, 

Minet's Production of Aluminum and its Industrial Use. (Waldo.). . . . i2mo, 

Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, 

Smith's Materials of Machines nmo, 

Thurston's Materials of Engineering. In Three Parts 8vo, 

Part II. Iron and Steel 8vo, 

Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents 8vo, 

Ulke's Modern Electrolytic Copper Refining 8vo, 



MINERALOGY. 

Barringer's Description of Minerals of Commercial Value. Oblong, morocco, 

Boyd's Resources of Southwest Virginia 8vo, 

Map of Southwest Virignia Pocket-book form. 

* Browning's Introduction to the Rarer Elements 8vo, 

Brush's Manual of Determinative Mineralogy. (Penfield.) 8vo, 

Chester's Catalogue of Minerals 8vo, paper. 

Cloth, 

Dictionary of the Names of Minerals 8vo, 

Dana's System of Mineralogy Large 8vo, half leather, 12 

First Appendix to Dana's New " System of Mineralogy." Large 8vo, 

Text-book of Mineralogy 8vo, 

Minerals and How to Study Them i2mo, 

Catalogue of American Localities of Minerals Large 8vo, 

Manual of Mineralogy and Petrography nmo 

Douglas's Untechnical Addresses on Technical Subjects nmo, 

Eakle's Mineral Tables 8vo, 

Egleston's Catalogue of Minerals and Synonyms 8vo, 

Goesel's Minerals and Metals : A Reference Book i6mo, mor. 

Groth's Introduction to Chemical Crystallography (Marshall) nmo, 

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Iddings's Rock Minerals 8vo, 

* Martin's Laboratory Guide to Qualitative Analysis with the Blowpipe. i2mo, 
Merrill's Non-metallic Minerals: Their Occurrence and Uses 8vo, 

Stones for Building and Decoration 8vo, 

* Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 

8vo, paper, 

* Richards's Synopsis of Mineral Characters i2mo, morocco, 

* Ries's Clays: Their Occurrence, Properties, and Uses 8vo, 

Rosenbusch's Microscopical Physiography of the Rock-making Minerals. 

(Iddings.) 8vo, 

* Tillman's Text-book of Important Minerals and Rocks 8vo, 



MINING. 

Boyd's Resources of Southwest Virginia 8vo. 3 ©c 

Map of Southwest Virginia Pocket-book form 2 00 

Douglas's Untechnical Addresses on Technical Subjects nmo. 1 00 

Eissler's Modern High Explosives , 8vr> 4 x; 

Goesel's Minerals and Metals : A Reference Book i6mo, mor. 3 00 

Goodyear's Coal-mines of the Western Coait of the United States nmo, 2 50 

Ihlseng's Manual of Mining 8vo, 5 00 

* Des's Lead-smelting nmo, 2 50 

Kunhardt's Practice of Ore Dressing in Europe 8vo, 1 50 

Miller's Cyanide Process nmo, 1 00 

O'Driscoll's Notes on the Treatment of Gold Ores 8vo, 2 00 

Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, 4 00 

* Walke's Lectures on Explosives 8vo, 4 00 

Weaver's Military Explosives 8vo, 3 00 

Wilson's Cyanide Processes nmo, 1 50 

Chlorination Process nmo, 1 50 

Hydraulic and Placer Mining nmo, 2 00 

Treatise on Practical and Theoretical Mine Ventilation nmo, 1 25 



SANITARY SCIENCE. 

Bashore's Sanitation of a Country House nmo, 

* Outlines of Practical Sanitation nmo, 

Folwell's Sewerage. (Designing, Construction, and Maintenance.). .... .8vo, 

Water-supply Engineering 8vo, 

Fowler's Sewage Works Analyses nmo, 

Fuertes's Water and Public Health nmo, 

Water-filtration Works nmo, 

Gerhard's Guide to Sanitary House-inspection iomo, 

Hazen's Filtration of Public Water-supplies 8vo, 

Leach's The Inspection and Analysis of Food with Special Reference to State 

Control 8vo, 

Mason's Water-supply. ( Considered principally from a Sanitary Standpoint) 8vo , 

Examination of Water. (Chemical and Bacteriological.) nmo, 

* Merriman's Elements of Sanitary Engineering 8vo, 

Ogden's Sewer Design nmo, 

Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- 
ence to Sanitary Water Analysis nmo, 

* Price's Handbook on Sanitation nmo, 

Richards's Cost of Food. A Study in Dietaries nmo, 

Cost of Living as Modified by Sanitary Science nmo, 

Cost of Shelter nmo, 

18 



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Richards^ WoodWs Air. Water, and Food from a Sanitary Stand- 

* Richards and Williams's' The Dietary' Computer « V °* 

Rideal's S wage and Bacterial Purification of Sewage «!?' 

Disinfection and the Preservation of Food e ' 

lurneaure and Russell's Public Water-supplies' " 



Whippl 



e s 



"• tc * supplies. . . . g vn 

iehring's Suppression of Tuberculosis. (Bolduan.) .' '. '. '. ' " ' ' " I2mo ' 
Microscopy of Drinking-water. . . c ' 

Winton's Microscopy of Vegetable Foods. . T 0> 

Woodhull's Notes on Military Hygiene . * Q> 

* Personal Hygiene l6mo > 

• • i2mo, 



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Emmons 



MISCELLANEOUS. 

's Geological Guide-book of the Rocky Mountain Excursion of the 
International Congress of Geologists. . . t °r 

Ferrel's Popular Treatise on the Winds. . ^ « V °' * 5 ° 

Gannett's Statistical Abstract of the World. 4 °° 

Haines's American Railway Management 24m ° 75 

Ricketts's History of Rensselaer Polytechnic Institute "1824-1804 ' Sm»nT°'' * 5 ° 

Rotherham's Emphasized New Testament. . 4 ° 4 ' '?*** 8 J°' 3 O0 

The World's Columbian Exposition of 1893 " ' S& 8 ™' 2 °° 

Winslow's Elements of Applied Microscopy 4 * X 0C 

* J i2mo. 1 5c 

HEBREW AND CHALDEE TEXT-BOOKS. 

Green's Elementary Hebrew Grammar 

Hebrew Chrestomathy. I2mo ' r 2 5 

Gesenius's Hebrew and Chaldee 'Lexicon 'to the' Old' Testament' Scripturls.* * °° 

Letteris's Hebrew^'ible! .' SmaU 4t °* half morocco > 5 00 

'" 19 8v <>' 2 25 



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